document_title: Morse code

question_text: what does dot dash dot mean in morse code

question_tokens: what does dot dash dot mean in morse code

text: Morse code

text: Development and history

text: Beginning in 1836, the American artist Samuel F. B. Morse, the American physicist Joseph Henry, and Alfred Vail developed an electrical telegraph system. This system sent pulses of electric current along wires which controlled an electromagnet that was located at the receiving end of the telegraph system. A code was needed to transmit natural language using only these pulses, and the silence between them. Around 1837, Morse, therefore, developed an early forerunner to the modern International Morse code. Around the same time, Carl Friedrich Gauss and Wilhelm Eduard Weber (1833) as well as Carl August von Steinheil (1837) had already used codes with varying word lengths for their telegraphs. Since around 1800, European experimenters had been making progress with earlier battery-powered signaling systems in emitting oxygen and hydrogen bubbles through liquid, flipping magnetic semaphore flags, tripping alarms across long distances over wire, and other techniques. The numerous ingenious experimental encoding designs they devised and demonstrated were telegraphic precursors to practical applications.[2]

text: In 1837, William Cooke and Charles Wheatstone in England began using an electrical telegraph that also used electromagnets in its receivers. However, in contrast with any system of making sounds of clicks, their system used pointing needles that rotated above alphabetical charts to indicate the letters that were being sent. In 1841, Cooke and Wheatstone built a telegraph that printed the letters from a wheel of typefaces struck by a hammer. This machine was based on their 1840 telegraph and worked well; however, they failed to find customers for this system and only two examples were ever built.[3]

text: On the other hand, the three Americans' system for telegraphy, which was first used in about 1844, was designed to make indentations on a paper tape when electric currents were received. Morse's original telegraph receiver used a mechanical clockwork to move a paper tape. When an electrical current was received, an electromagnet engaged an armature that pushed a stylus onto the moving paper tape, making an indentation on the tape. When the current was interrupted, a spring retracted the stylus, and that portion of the moving tape remained unmarked.

text: The Morse code was developed so that operators could translate the indentations marked on the paper tape into text messages. In his earliest code, Morse had planned to transmit only numerals, and to use a codebook to look up each word according to the number which had been sent. However, the code was soon expanded by Alfred Vail in 1840 to include letters and special characters, so it could be used more generally. Vail estimated the frequency of use of letters in the English language by counting the movable type he found in the type-cases of a local newspaper in Morristown.[4]  The shorter marks were called "dots", and the longer ones "dashes", and the letters most commonly used were assigned the shorter sequences of dots and dashes. This code was used since 1844 and became known as Morse landline code or American Morse code.

text: In the original Morse telegraphs, the receiver's armature made a clicking noise as it moved in and out of position to mark the paper tape. The telegraph operators soon learned that they could translate the clicks directly into dots and dashes, and write these down by hand, thus making the paper tape unnecessary. When Morse code was adapted to radio communication, the dots and dashes were sent as short and long tone pulses. It was later found that people become more proficient at receiving Morse code when it is taught as a language that is heard, instead of one read from a page.[5]

text: To reflect the sounds of Morse code receivers, the operators began to vocalize a dot as "dit", and a dash as "dah". Dots which are not the final element of a character became vocalized as "di". For example, the letter "c" was then vocalized as "dah-di-dah-dit".[6][7] Morse code was sometimes facetiously known as "iddy-umpty", and a dash as "umpty", leading to the word "umpteen".[8]

text: The Morse code, as it is used internationally today, was derived from a much refined proposal which became known as "Hamburg alphabet" by Friedrich Clemens Gerke in 1848. It was adopted by the Deutsch-Österreichischer Telegraphenverein (German-Austrian Telegraph Society) in 1851. This finally led to the International Morse code in 1865.

text: In the 1890s, Morse code began to be used extensively for early radio communication, before it was possible to transmit voice. In the late 19th and early 20th centuries, most high-speed international communication used Morse code on telegraph lines, undersea cables and radio circuits. In aviation, Morse code in radio systems started to be used on a regular basis in the 1920s. Although previous transmitters were bulky and the spark gap system of transmission was difficult to use, there had been some earlier attempts. In 1910, the US Navy experimented with sending Morse from an airplane.[9] That same year, a radio on the airship America had been instrumental in coordinating the rescue of its crew.[10] Zeppelin airships equipped with radio were used for bombing and naval scouting during World War I,[11] and ground-based radio direction finders were used for airship navigation.[11] Allied airships and military aircraft also made some use of radiotelegraphy. However, there was little aeronautical radio in general use during World War I, and in the 1920s, there was no radio system used by such important flights as that of Charles Lindbergh from New York to Paris in 1927. Once he and the Spirit of St. Louis were off the ground, Lindbergh was truly alone and incommunicado. On the other hand, when the first airplane flight was made from California to Australia in 1928 on the Southern Cross, one of its four crewmen was its radio operator who communicated with ground stations via radio telegraph.

text: Beginning in the 1930s, both civilian and military pilots were required to be able to use Morse code, both for use with early communications systems and for identification of navigational beacons which transmitted continuous two- or three-letter identifiers in Morse code. Aeronautical charts show the identifier of each navigational aid next to its location on the map.

text: Radiotelegraphy using Morse code was vital during World War II, especially in carrying messages between the warships and the naval bases of the belligerents. Long-range ship-to-ship communication was by radio telegraphy, using encrypted messages because the voice radio systems on ships then were quite limited in both their range and their security. Radiotelegraphy was also extensively used by warplanes, especially by long-range patrol planes that were sent out by those navies to scout for enemy warships, cargo ships, and troop ships.

text: In addition, rapidly moving armies in the field could not have fought effectively without radiotelegraphy because they moved more rapidly than telegraph and telephone lines could be erected. This was seen especially in the blitzkrieg offensives of the Nazi German Wehrmacht in Poland, Belgium, France (in 1940), the Soviet Union, and in North Africa; by the British Army in North Africa, Italy, and the Netherlands; and by the U.S. Army in France and Belgium (in 1944), and in southern Germany in 1945.

text: Morse code was used as an international standard for maritime distress until 1999 when it was replaced by the Global Maritime Distress Safety System. When the French Navy ceased using Morse code on January 31, 1997, the final message transmitted was "Calling all. This is our last cry before our eternal silence."[12] In the United States the final commercial Morse code transmission was on July 12, 1999, signing off with Samuel Morse's original 1844 message, "What hath God wrought", and the prosign "SK".[13]

text: As of 2015, the United States Air Force still trains ten people a year in Morse.[14]  The United States Coast Guard has ceased all use of Morse code on the radio, and no longer monitors any radio frequencies for Morse code transmissions, including the international medium frequency (MF) distress frequency of 500 kHz.[15] However, the Federal Communications Commission still grants commercial radiotelegraph operator licenses to applicants who pass its code and written tests.[16] Licensees have reactivated the old California coastal Morse station KPH and regularly transmit from the site under either this Call sign or as KSM. Similarly, a few US Museum ship stations are operated by Morse enthusiasts.[17]

text: User proficiency

text: Morse code speed is measured in words per minute (wpm) or characters per minute (cpm). Characters have differing lengths because they contain differing numbers of dots and dashes.  Consequently, words also have different lengths in terms of dot duration, even when they contain the same number of characters.  For this reason, a standard word is helpful to measure operator transmission speed. "PARIS" and "CODEX" are two such standard words.[18] Operators skilled in Morse code can often understand ("copy") code in their heads at rates in excess of 40 wpm.

text: In addition to knowing, understanding, and being able to copy the standard written alpha-numeric and punctuation characters or symbols at high speeds, skilled high speed operators must also be fully knowledgeable of all of the special unwritten Morse code symbols for the standard Prosigns for Morse code and the meanings of these special procedural signals in standard Morse code communications protocol.

text: International contests in code copying are still occasionally held. In July 1939 at a contest in Asheville, North Carolina in the United States Ted R. McElroy set a still-standing record for Morse copying, 75.2 wpm.[19] William Pierpont N0HFF also notes that some operators may have passed 100 wpm.[19] By this time, they are "hearing" phrases and sentences rather than words. The fastest speed ever sent by a straight key was achieved in 1942 by Harry Turner W9YZE (d. 1992) who reached 35 wpm in a demonstration at a U.S. Army base.  To accurately compare code copying speed records of different eras it is useful to keep in mind that different standard words (50 dot durations versus 60 dot durations) and different interword gaps (5 dot durations versus 7 dot durations) may have been used when determining such speed records.  For example, speeds run with the CODEX standard word and the PARIS standard may differ by up to 20%.

text: Today among amateur operators there are several organizations that recognize high-speed code ability, one group consisting of those who can copy Morse at 60 wpm.[20]  Also, Certificates of Code Proficiency are issued by several amateur radio societies, including the American Radio Relay League.  Their basic award starts at 10 wpm with endorsements as high as 40 wpm, and are available to anyone who can copy the transmitted text.  Members of the Boy Scouts of America may put a Morse interpreter's strip on their uniforms if they meet the standards for translating code at 5 wpm.

text: International Morse Code

text: Morse code has been in use for more than 160 years—longer than any other electrical coding system. What is called Morse code today is actually somewhat different from what was originally developed by Vail and Morse. The Modern International Morse code, or continental code, was created by Friedrich Clemens Gerke in 1848 and initially used for telegraphy between Hamburg and Cuxhaven in Germany. Gerke changed nearly half of the alphabet and all of the numerals, providing the foundation for the modern form of the code. After some minor changes, International Morse Code was standardized at the International Telegraphy Congress in 1865 in Paris and was later made the standard by the International Telecommunication Union (ITU). Morse's original code specification, largely limited to use in the United States and Canada, became known as American Morse code or railroad code. American Morse code is now seldom used except in historical re-enactments.

text: Aviation

text: In aviation, pilots use radio navigation aids. To ensure that the stations the pilots are using are serviceable, the stations transmit a  set of identification letters (usually a two-to-five-letter version of the station name) in Morse code. Station identification letters are shown on air navigation charts. For example, the VOR-DME based at Vilo Acuña Airport in Cayo Largo del Sur, Cuba is coded as "UCL", and UCL in Morse code is transmitted on its radio frequency. In some countries, during periods of maintenance, the facility may radiate a T-E-S-T code (▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄)  or the code may be removed which tells pilots and navigators that the station is unreliable.  In Canada, the identification is removed entirely to signify the navigation aid is not to be used.[21][22]  In the aviation service, Morse is typically sent at a very slow speed of about 5 words per minute.  In the U.S., pilots do not actually have to know Morse to identify the transmitter because the dot/dash sequence is written out next to the transmitter's symbol on aeronautical charts.  Some modern navigation receivers automatically translate the code into displayed letters.

text: Amateur radio

text: International Morse code today is most popular among amateur radio operators, in the mode commonly referred to as "continuous wave" or "CW". (This name was chosen to distinguish it from the damped wave emissions from spark transmitters, not because the transmission is continuous.) Other keying methods are available in radio telegraphy, such as frequency shift keying.

text: The original amateur radio operators used Morse code exclusively since voice-capable radio transmitters did not become commonly available until around 1920. Until 2003, the International Telecommunication Union mandated Morse code proficiency as part of the amateur radio licensing procedure worldwide. However, the World Radiocommunication Conference of 2003 made the Morse code requirement for amateur radio licensing optional.[24] Many countries subsequently removed the Morse requirement from their licence requirements.[25]

text: Until 1991, a demonstration of the ability to send and receive Morse code at a minimum of five words per minute (wpm) was required to receive an amateur radio license for use in the United States from the Federal Communications Commission. Demonstration of this ability was still required for the privilege to use the HF bands. Until 2000, proficiency at the 20 wpm level was required to receive the highest level of amateur license (Amateur Extra Class); effective April 15, 2000, the FCC reduced the Extra Class requirement to five wpm.[26] Finally, effective on February 23, 2007, the FCC eliminated the Morse code proficiency requirements from all amateur radio licenses.

text: While voice and data transmissions are limited to specific amateur radio bands under U.S. rules, Morse code is permitted on all amateur bands—LF, MF, HF, VHF, and UHF. In some countries, certain portions of the amateur radio bands are reserved for transmission of Morse code signals only.

text: The relatively limited speed at which Morse code can be sent led to the development of an extensive number of abbreviations to speed communication. These include prosigns, Q codes, and a set of Morse code abbreviations for typical message components. For example, CQ is broadcast to be interpreted as "seek you" (I'd like to converse with anyone who can hear my signal). OM (old man), YL (young lady) and XYL ("ex-YL" – wife) are common abbreviations. YL or OM is used by an operator when referring to the other operator, XYL or OM is used by an operator when referring to his or her spouse. QTH is "location" ("My QTH" is "My location"). The use of abbreviations for common terms permits conversation even when the operators speak different languages.

text: Although the traditional telegraph key (straight key) is still used by some amateurs, the use of mechanical semi-automatic keyers (known as "bugs") and of fully automatic electronic keyers is prevalent today. Software is also frequently employed to produce and decode Morse code radio signals.

text: Many amateur radio repeaters identify with Morse, even though they are used for voice communications.

text: Other uses

text: Through May 2013, the First, Second, and Third Class (commercial) Radiotelegraph Licenses using code tests based upon the CODEX standard word were still being issued in the United States by the Federal Communications Commission.  The First Class license required 20 WPM code group and 25 WPM text code proficiency, the others 16 WPM code group test (five letter blocks sent as simulation of receiving encrypted text) and 20 WPM code text (plain language) test.  It was also necessary to pass written tests on operating practice and electronics theory.  A unique additional demand for the First Class was a requirement of a year of experience for operators of shipboard and coast stations using Morse.  This allowed the holder to be chief operator on board a passenger ship.  However, since 1999 the use of satellite and very high-frequency maritime communications systems (GMDSS) has made them obsolete.  (By that point meeting experience requirement for the First was very difficult.)  Currently, only one class of license, the Radiotelegraph Operator License, is issued.  This is granted either when the tests are passed or as the Second and First are renewed and become this lifetime license.  For new applicants, it requires passing a written examination on electronic theory and radiotelegraphy practices, as well as 16 WPM codegroup and 20 WPM text tests.  However, the code exams are currently waived for holders of Amateur Extra Class licenses who obtained their operating privileges under the old 20 WPM test requirement.

text: Radio navigation aids such as VORs and NDBs for aeronautical use broadcast identifying information in the form of Morse Code, though many VOR stations now also provide voice identification.[27] Warships, including those of the U.S. Navy, have long used signal lamps to exchange messages in Morse code. Modern use continues, in part, as a way to communicate while maintaining radio silence.

text: ATIS (Automatic Transmitter Identification System) uses Morse code to identify uplink sources of analog satellite transmissions.

text: Applications for the general public

text: An important application is signalling for help through SOS, "▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄". This can be sent many ways: keying a radio on and off, flashing a mirror, toggling a flashlight, and similar methods.  SOS is not three separate characters, rather, it is a prosign SOS, and is keyed without gaps between characters.[28]

text: Some Nokia mobile phones offer an option to alert the user of an incoming text message with the Morse tone "▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄" (representing SMS or Short Message Service).[29]  In addition, applications are now available for mobile phones that enable short messages to be input in Morse Code.[30]

text: Morse code as an assistive technology

text: Morse code has been employed as an assistive technology, helping people with a variety of disabilities to communicate. Morse can be sent by persons with severe motion disabilities, as long as they have some minimal motor control. An original solution to the problem that caretakers have to learn to decode has been an electronic typewriter with the codes written on the keys. Codes were sung by users; see the voice typewriter employing morse or votem, Newell and Nabarro, 1968.

text: Morse code can also be translated by computer and used in a speaking communication aid. In some cases, this means alternately blowing into and sucking on a plastic tube ("sip-and-puff" interface). An important advantage of Morse code over row column scanning is that once learned, it does not require looking at a display. Also, it appears faster than scanning.

text: In one case reported in the radio amateur magazine QST,[31] an old shipboard radio operator who had a stroke and lost the ability to speak or write could communicate with his physician (a radio amateur) by blinking his eyes in Morse. Two examples of communication in intensive care units were also published in QST, [32][33]  Another example occurred in 1966 when prisoner of war Jeremiah Denton, brought on television by his North Vietnamese captors, Morse-blinked the word TORTURE. In these two cases, interpreters were available to understand those series of eye-blinks.

text: Representation, timing, and speeds

text:
A sample Morse code transmission

The text "Welcome to Wikipedia, the free encyclopedia that anyone can edit." sent as Morse code at 13 wpm.
Problems playing this file? See media help.

text:
Morse code A through Z

"A B C D E F G H I J K L M N O P Q R S T U V W X Y Z" in Morse code at 8 wpm.
Problems playing this file? See media help.

text: This section includes inline links to audio files. If you have trouble playing the files, see Wikipedia Media help.

text: International Morse code is composed of five elements:[1]

text:
short mark, dot or "dit" (▄▄▄▄): "dot duration" is one time unit long
longer mark, dash or "dah" (▄▄▄▄▄▄): three time units long
inter-element gap between the dots and dashes within a character: one dot duration or one unit long
short gap (between letters): three time units long
medium gap (between words): seven time units long

tag: ol

text: Transmission

text: Morse code can be transmitted in a number of ways: originally as electrical pulses along a telegraph wire, but also as an audio tone, a radio signal with short and long tones, or as a mechanical, audible, or visual signal (e.g. a flashing light) using devices like an Aldis lamp or a heliograph, a common flashlight, or even a car horn.  Some mine rescues have used pulling on a rope - a short pull for a dot and a long pull for a dash.

text: Morse code is transmitted using just two states (on and off). Historians have called it the first digital code. Morse code may be represented as a binary code, and that is what telegraph operators do when transmitting messages. Working from the above ITU definition and further defining a bit as a dot time, a Morse code sequence may be made from a combination of the following five-bit strings:

text:
short mark, dot or "dit" (▄▄▄▄): 1
longer mark, dash or "dah" (▄▄▄▄▄▄): 111
intra-character gap (between the dots and dashes within a character): 0
short gap (between letters): 000
medium gap (between words): 0000000

text: Note that the marks and gaps alternate: dots and dashes are always separated by one of the gaps, and that the gaps are always separated by a dot or a dash.

text: Morse messages are generally transmitted by a hand-operated device such as a telegraph key, so there are variations introduced by the skill of the sender and receiver — more experienced operators can send and receive at faster speeds. In addition, individual operators differ slightly, for example, using slightly longer or shorter dashes or gaps, perhaps only for particular characters. This is called their "fist", and experienced operators can recognize specific individuals by it alone.  A good operator who sends clearly and is easy to copy is said to have a "good fist".  A "poor fist" is a characteristic of sloppy or hard to copy Morse code.

text: Cable code

text: The very long time constants of 19th and early 20th century submarine communications cables required a different form of Morse signalling. Instead of keying a voltage on and off for varying times, the dits and dahs were represented by two polarities of voltage impressed on the cable, for a uniform time.[34]

text: Timing

text: Below is an illustration of timing conventions. The phrase "MORSE CODE", in Morse code format, would normally be written something like this, where – represents dahs and · represents dits:

text: Next is the exact conventional timing for this phrase, with = representing "signal on", and . representing "signal off", each for the time length of exactly one dit:

text: Spoken representation

text: Morse code is often spoken or written with "dah" for dashes, "dit" for dots located at the end of a character, and "di" for dots located at the beginning or internally within the character. Thus, the following Morse code sequence:

text: is orally:

text: Dah-dah       dah-dah-dah       di-dah-dit       di-di-dit dit,       Dah-di-dah-dit       dah-dah-dah       dah-di-dit dit.

text: There is little point in learning to read written Morse as above; rather, the sounds of all of the letters and symbols need to be learned, for both sending and receiving.

text: Speed in words per minute

text: All Morse code elements depend on the dot length. A dash is the length of 3 dots, and spacings are specified in number of dot lengths. An unambiguous method of specifying the transmission speed is to specify the dot duration as, for example, 50 milliseconds.

text: Specifying the dot duration is, however, not the common practice. Usually, speeds are stated in words per minute. That introduces ambiguity because words have different numbers of characters, and characters have different dot lengths.  It is not immediately clear how a specific word rate determines the dot duration in milliseconds.

text: Some method to standardize the transformation of a word rate to a dot duration is useful.  A simple way to do this is to choose a dot duration that would send a typical word the desired number of times in one minute.  If, for example, the operator wanted a character speed of 13 words per minute, the operator would choose a dot rate that would send the typical word 13 times in exactly one minute.

text: The typical word thus determines the dot length.  It is common to assume that a word is 5 characters long.  There are two common typical words: "PARIS" and "CODEX".  PARIS mimics a word rate that is typical of natural language words and reflects the benefits of Morse code's shorter code durations for common characters such as "e" and "t".  CODEX offers a word rate that is typical of 5-letter code groups (sequences of random letters). Using the word PARIS as a standard, the number of dot units is 50 and a simple calculation shows that the dot length at 20 words per minute is 60 milliseconds.  Using the word CODEX with 60 dot units, the dot length at 20 words per minute is 50 milliseconds.

text: Because Morse code is usually sent by hand, it is unlikely that an operator could be that precise with the dot length, and the individual characteristics and preferences of the operators usually override the standards.

text: For commercial radiotelegraph licenses in the United States, the Federal Communications Commission specifies tests for Morse code proficiency in words per minute and in code groups per minute.[35] The Commission specifies that a word is 5 characters long.  The Commission specifies Morse code test elements at 16 code groups per minute, 20 words per minute, 20 code groups per minute, and 25 words per minute.[36] The word per minute rate would be close to the PARIS standard, and the code groups per minute would be close to the CODEX standard.

text: While the Federal Communications Commission no longer requires Morse code for amateur radio licenses, the old requirements were similar to the requirements for commercial radiotelegraph licenses.[37]

text: A difference between amateur radio licenses and commercial radiotelegraph licenses is that commercial operators must be able to receive code groups of random characters along with plain language text.  For each class of license, the code group speed requirement is slower than the plain language text requirement. For example, for the Radiotelegraph Operator License, the examinee must pass a 20 word per minute plain text test and a 16 word per minute code group test.[16]

text: Based upon a 50 dot duration standard word such as PARIS, the time for one dot duration or one unit can be computed by the formula:

text: Where: T is the unit time, or dot duration in milliseconds, and W is the speed in wpm.

text: High-speed telegraphy contests are held; according to the Guinness Book of Records in June 2005 at the International Amateur Radio Union's 6th World Championship in High Speed Telegraphy in Primorsko, Bulgaria, Andrei Bindasov of Belarus transmitted 230 morse code marks of mixed text in one minute.[38]

text: Farnsworth speed

text: Sometimes, especially while teaching Morse code, the timing rules above are changed so two different speeds are used: a character speed and a text speed. The character speed is how fast each individual letter is sent.  The text speed is how fast the entire message is sent.  For example, individual characters may be sent at a 13 words-per-minute rate, but the intercharacter and interword gaps may be lengthened so the word rate is only 5 words per minute.

text: Using different character and text speeds is, in fact, a common practice, and is used in the Farnsworth method of learning Morse code.

text: Alternative display of common characters in International Morse code

text: Some methods of teaching Morse code use a dichotomic search table.

text: Link budget issues

text: Morse Code cannot be treated as a classical radioteletype (RTTY) signal when it comes to calculating a link margin or a link budget for the simple reason of it possessing variable length dots and dashes as well as variant timing between letters and words. For the purposes of Information Theory and Channel Coding comparisons, the word PARIS is used to determine Morse Code's properties because it has an even number of dots and dashes.

text: Morse Code, when transmitted essentially, creates an AM signal (even in on/off keying mode), assumptions about signal can be made with respect to similarly timed RTTY signalling. Because Morse code transmissions employ an on-off keyed radio signal, it requires less complex transmission equipment than other forms of radio communication.

text: Morse code also requires less signal bandwidth than voice communication, typically 100–150 Hz, compared to the roughly 2400 Hz used by single-sideband voice, although at a lower data rate.

text: Morse code is usually heard at the receiver as a medium-pitched on/off audio tone (600–1000 Hz), so transmissions are easier to copy than voice through the noise on congested frequencies, and it can be used in very high noise / low signal environments. The transmitted power is concentrated into a limited bandwidth so narrow receiver filters can be used to suppress interference from adjacent frequencies. The audio tone is usually created by use of a beat frequency oscillator.

text: The narrow signal bandwidth also takes advantage of the natural aural selectivity of the human brain, further enhancing weak signal readability. This efficiency makes CW extremely useful for DX (distance) transmissions, as well as for low-power transmissions (commonly called "QRP operation", from the Q-code for "reduce power").

text: The ARRL has a readability standard for robot encoders called ARRL Farnsworth Spacing[39] that is supposed to have higher readability for both robot and human decoders. Some programs like WinMorse[40] have implemented the standard.

text: Learning methods

text: People learning Morse code using the Farnsworth method are taught to send and receive letters and other symbols at their full target speed, that is with normal relative timing of the dots, dashes, and spaces within each symbol for that speed. The Farnsworth method is named for Donald R. "Russ" Farnsworth, also known by his call sign, W6TTB. However, initially exaggerated spaces between symbols and words are used, to give "thinking time" to make the sound "shape" of the letters and symbols easier to learn. The spacing can then be reduced with practice and familiarity.

text: Another popular teaching method is the Koch method, named after German psychologist Ludwig Koch, which uses the full target speed from the outset but begins with just two characters. Once strings containing those two characters can be copied with 90% accuracy, an additional character is added, and so on until the full character set is mastered.

text: In North America, many thousands of individuals have increased their code recognition speed (after initial memorization of the characters) by listening to the regularly scheduled code practice transmissions broadcast by W1AW, the American Radio Relay League's headquarters station.[citation needed]

text: Mnemonics

text: Visual mnemonic charts have been devised over the ages. Baden-Powell included one in the Girl Guides handbook[41] in 1918.

text: In the United Kingdom, many people learned the Morse code by means of a series of words or phrases that have the same rhythm as a Morse character. For instance, "Q" in Morse is dah-dah-di-dah, which can be memorized by the phrase "God save the Queen", and the Morse for "F" is di-di-dah-dit, which can be memorized as "Did she like it."

text: A well-known Morse code rhythm from the Second World War period derives from Beethoven's Fifth Symphony, the opening phrase of which was regularly played at the beginning of BBC broadcasts. The timing of the notes corresponds to the Morse for "V", di-di-di-dah, understood as "V for Victory" (as well as the Roman numeral for the number five).[42][43]

text: Letters, numbers, punctuation, prosigns for Morse code and non-English variants

text:
Category
Character
Code

Letters
A, a

▄▄▄▄▄▄▄▄

Letters
B, b

▄▄▄▄▄▄▄▄▄▄▄▄

Letters
C, c

− · − ·

Letters
D, d

 − · ·

Letters
E, e

 ·

Letters
F, f

· · − ·

Letters
G, g

− − ·

Letters
H, h

· · · ·

Letters
I, i

· ·

Letters
J, j

· − − −

Letters
K, kProsign for "Invitation to transmit"

− · −

Letters
L, l

· − · ·

Letters
M, m

− −

Letters
N, n

− ·

Letters
O, o

− − −

Letters
P, p

 · − − ·

Letters
Q, q

 − − · −

Letters
R, r

 · − ·

Letters
S, s

 · · ·

Letters
T, t

 −

Letters
U, u

 · · −

Letters
V, v

 · · · −

Letters
W, w

 · − −

Letters
X, x

 − · · −

Letters
Y, y

 − · − −

Letters
Z, z

 − − · ·

Numbers
0

 − − − − −

Numbers
1

· − − − −

Numbers
2

· · − − −

Numbers
3

· · · − −

Numbers
4

· · · · −

Numbers
5

· · · · ·

Numbers
6

− · · · ·

Numbers
7

− − · · ·

Numbers
8

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Numbers
9

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Punctuation
Period [.]

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Punctuation
Comma [,]

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Punctuation
Question Mark [?]

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Punctuation
Apostrophe [']

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Punctuation
Exclamation Point [!] KW digraph Not in ITU-R recommendation

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Punctuation
Slash/Fraction Bar [/]

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Punctuation
 Parenthesis (Open)

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Punctuation
 Parenthesis (Close)

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Punctuation
 Ampersand (or "Wait") [&] AS digraphProsign for "WAIT"

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Punctuation
 Colon [:]

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Punctuation
 Semicolon [;]   Not in ITU-R ITU-R M.1172 or ITU-R M.1677-1

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Punctuation
 Double Dash [=]

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Punctuation
 Plus sign [+]

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Punctuation
Hyphen,  Minus Sign [-]

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Punctuation
Underscore [_]  Not in ITU-R ITU-R M.1172 or ITU-R M.1677-1

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Punctuation
Quotation mark ["]

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Punctuation
Dollar sign [$]  SX digraph Not in ITU-R ITU-R M.1172 or ITU-R M.1677-1

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Punctuation
At Sign [@]   AC digraph

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Prosigns
End of work

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Prosigns
Error

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Prosigns
Invitation to Transmit  Also used for K

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Prosigns
Starting Signal

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Prosigns
New Page Signal  AR digraphMessage separatorSingle-line display may use printed "+"

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Prosigns
Understood  Also used for Ŝ

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Prosigns
Wait  also used for Ampersand [&]

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Non-English extensions
À, à  Shared by À, Å

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Non-English extensions
Ä, ä  Shared by Ä, Æ, Ą

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Non-English Extensions
Å, å  Shared by À, Å

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Non-English extensions
Ą, ą  Shared by Ä, Æ, Ą

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Non-English extensions
Æ, æ  Shared by Ä, Æ, Ą

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Non-English extensions
Ć, ć  Shared by Ć, Ĉ, Ç

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Non-English extensions
Ĉ, ĉ  Shared by Ć, Ĉ, Ç

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Non-English Extensions
Ç, ç  Shared by Ć, Ĉ, Ç

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Non-English extensions
CH, ch  Shared by CH, Ĥ, Š

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Non-English extensions
Đ, đ  Shared by Đ, É, ĘNot to be confused with Eth (Ð, ð)(É is the only accented character included in ITU-R recommendation)

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Non-English extensions
Ð, ð   Not to be confused with D with stroke (Đ, đ)

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Non-English extensions
É, é  Shared by Đ, É, Ę (É is the only accented character included in ITU-R recommendation)

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Non-English extensions
È, è  Shared by È, Ł

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Non-English extensions
Ę, ę  Shared by Đ, É, Ę (É is the only accented character included in ITU-R recommendation)

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Non-English extensions
Ĝ, ĝ

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Non-English extensions
Ĥ, ĥ  Shared by CH, Ĥ, Š

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Non-English extensions
Ĵ, ĵ

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Non-English extensions
Ł, ł  Shared by È, Ł

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Non-English extensions
Ń, ń  Shared by Ń, Ñ

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Non-English extensions
Ñ, ñ  Shared by Ń, Ñ

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Non-English extensions
Ó, ó  Shared by Ó, Ö, Ø

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Non-English extensions
Ö, ö  Shared by Ó, Ö, Ø

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Non-English extensions
Ø, ø   Shared by Ó, Ö, Ø

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Non-English extensions
Ś, ś

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Non-English extensions
Ŝ, ŝ  Prosign for "Understood"

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Non-English extensions
Š, š  Shared by CH, Ĥ, Š

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Non-English extensions
Þ, þ

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Non-English extensions
Ü, ü  Shared by Ü, Ŭ

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Non-English extensions
Ŭ, ŭ   Shared by Ü, Ŭ

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Non-English extensions
Ź, ź

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Non-English extensions
Ż, ż

− − · · −

text: Prosigns

text: Prosigns for Morse code are special (usually) unwritten procedural signals or symbols that are used to indicate changes in communications protocol status or white space text formatting actions.

text: Symbol representations

text: The symbols !, $ and & are not defined inside the ITU recommendation on Morse code, but conventions for them exist. The @ symbol was formally added in 2004.

text: There is no standard representation for the exclamation mark (!), although the KW digraph (▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄) was proposed in the 1980s by the Heathkit Company (a vendor of assembly kits for amateur radio equipment).

text: While Morse code translation software prefers the Heathkit version, on-air use is not yet universal as some amateur radio operators in North America and the Caribbean continue to prefer the older MN digraph (▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄) carried over from American landline telegraphy code.

text:
The ITU has never codified formal Morse Code representations for currencies as the ISO 4217 Currency Codes are preferred for transmission.
The $ sign code was represented in the Phillips Code, a huge collection of abbreviations used on land line telegraphy, as SX.

text: The representation of the & sign given above, often shown as AS, is also the Morse prosign for wait. In addition, the American landline representation of an ampersand was similar to "ES" (▄▄▄▄▄▄▄▄▄▄▄) and hams have carried over this usage as a synonym for "and" (WX HR COLD ES RAINY, "the weather here is cold & rainy").

text:
On May 24, 2004 — the 160th anniversary of the first public Morse telegraph transmission — the Radiocommunication Bureau of the International Telecommunication Union (ITU-R) formally added the @ ("commercial at" or "commat") character to the official Morse character set, using the sequence denoted by the AC digraph (▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄).
This sequence was reportedly chosen to represent "A[T] C[OMMERCIAL]" or a letter "a" inside a swirl represented by a "C".[44] The new character facilitates sending email addresses by Morse code and is notable since it is the first official addition to the Morse set of characters since World War I.

text: Non-Latin extensions

text: For Chinese, Chinese telegraph code is used to map Chinese characters to four-digit codes and send these digits out using standard Morse code. Korean Morse code uses the SKATS mapping, originally developed to allow Korean to be typed on western typewriters. SKATS maps hangul characters to arbitrary letters of the Latin script and has no relationship to pronunciation in Korean. For Russian and Bulgarian, Russian Morse code is used to map the Cyrillic characters to four-element codes. Many of the characters are encoded the same way (A, O, E, I, T, M, N, R, K, etc.). Bulgarian alphabet contains 30 characters, which exactly match all possible combinations of 1, 2, 3, and 4 dots and dashes. Russian requires 1 extra character, "Ы"  which is encoded with 5 elements.

text: Unusual variants

text: During early World War I (1914–1916), Germany briefly experimented with 'dotty' and 'dashy' Morse, in essence adding a dot or a dash at the end of each Morse symbol. Each one was quickly broken by Allied SIGINT, and standard Morse was restored by Spring 1916. Only a small percentage of Western Front (North Atlantic and Mediterranean Sea) traffic was in 'dotty' or 'dashy' Morse during the entire war. In popular culture, this is mostly remembered in the book The Codebreakers by Kahn and in the national archives of the UK and Australia (whose SIGINT operators copied most of this Morse variant). Kahn's cited sources come from the popular press and wireless magazines of the time.[45]

text: Other forms of 'Fractional Morse' or 'Fractionated Morse' have emerged.[46]

text: Decoding software

text: Decoding software for Morse code ranges from software-defined wide-band radio receivers coupled to the Reverse Beacon Network,[47] which decodes signals and detects CQ messages on ham bands, to smartphone applications.[48]


document_title: Caesarean section

question_text: what is the mortality rate for c sections

question_tokens: what is the mortality rate for c sections

root

text: Caesarean section

text: Uses[edit]

text: Caesarean section is recommended when vaginal delivery might pose a risk to the mother or baby. C-sections are also carried out for personal and social reasons. Systematic reviews have found no strong evidence about the impact of caesareans for non-medical reasons.[10][11] Recommendations encourage counseling to identify the reasons for the request, addressing anxieties and information, and encouraging vaginal birth.[10][12] Elective caesareans at 38 weeks showed increased health complications in the newborn.[13] For this reason, planned caesarean sections (also known as elective caesarean sections) should not be scheduled before 39 weeks gestation unless there is medical reason to do so.

tag: p

text: Medical uses[edit]

text: Complications of labour and factors increasing the risk associated with vaginal delivery, such as:

text:
abnormal presentation (breech or transverse positions). Babies are usually born head first. If the baby is in another position the birth may be complicated. In a ‘breech presentation’ the unborn baby is bottom-down instead of head-down. Babies born bottom-first are more likely to be harmed during a normal (vaginal) birth than those born head-first. For instance, the baby might not get enough oxygen during the birth. Having a planned caesarean may reduce these problems. A review looking at planned caesarean section for singleton breech presentation with planned vaginal birth, concludes that in the short term, births with a planned caesarean were safer for babies than vaginal births. Fewer babies died or were seriously hurt when they were born by caesarean. However, there was tentative evidence that children who were born by caesarean had more health problems at age two. Caesareans caused some short-term problems for mothers such as more abdominal pain. They also had some benefits, such as less urinary incontinence and less perineal pain.[14]
prolonged labour or a failure to progress (dystocia)
fetal distress
cord prolapse
uterine rupture or an elevated risk thereof
hypertension in the mother or baby after amniotic rupture (the waters breaking)
tachycardia in the mother or baby after amniotic rupture (the waters breaking)
placenta problems (placenta praevia, placental abruption or placenta accreta)
failed labour induction
failed instrumental delivery (by forceps or ventouse (Sometimes a trial of forceps/ventouse delivery is attempted, and if unsuccessful, the baby will need to be born by caesarean section.)
large baby weighing > 4,000 grams (macrosomia)
umbilical cord abnormalities (vasa previa, multilobate including bilobate and succenturiate-lobed placentas, velamentous insertion)

tag: ul

text: Other complications of pregnancy, pre-existing conditions and concomitant disease, such as:

text:
pre-eclampsia[15]
previous (high risk) fetus
HIV infection of the mother with a high viral load (HIV with a low maternal viral load is not necessarily an indication for caesarean section)
Sexually transmitted diseases, such as a first outbreak of genital herpes very recently before the onset of labor (which can cause infection in the baby if born vaginally)
previous classical (longitudinal) Caesarean section
previous uterine rupture
prior problems with the healing of the perineum (from previous childbirth or Crohn's disease)
Bicornuate uterus
Rare cases of posthumous birth after the death of the mother

text: Other

text: Decreasing experience of accoucheurs with management of the breech presentation — Although obstetricians and midwives are extensively trained in proper procedures for breach presentation deliveries using simulation mannequins, there is decreasing experience with actual vaginal breech delivery which may increase the risk further.[16]

text: Prevention[edit]

text: It is generally agreed that the prevalence of caesarean section is higher than needed in many countries and physicians are encouraged to actively lower the rate, as a caesarean rate higher than 10-15% is not associated with reductions in maternal or infant mortality rates.[4] Some evidence supports a higher rate of 19% may result in better outcomes.[8]

text: Some of these efforts are: emphasizing a long latent phase of labor is not abnormal and not a justification for C-section; a new definition of the start of active labor from a cervical dilatation of 4 cm to a dilatation of 6 cm; and allowing at least 2 hours of pushing for women who have previously given birth and 3 hours of pushing for women who have not previously given birth before labor arrest is considered.[3] Physical exercise during pregnancy also decreases the risk.[17]

text: Risks[edit]

text: Adverse outcomes in low risk pregnancies occur in 8.6% of vaginal deliveries and 9.2% of caesarean section deliveries.[3]

text: Mother[edit]

text: In those who are low risk, the risk of death for caesarean sections is 13 per 100,000 and for vaginal birth 3.5 per 100,000 in the developed world.[3] The United Kingdom National Health Service gives the risk of death for the mother as three times that of a vaginal birth [18] but it is important to remember the actual risk of death in either situation is extremely small in resource-rich settings.

text: In Canada the difference in serious morbidity or mortality for the mother (e.g. cardiac arrest, wound hematoma, or hysterectomy) was 1.8 additional cases per 100 or three times the risk.[19]

text: A caesarean section is associated with risks of postoperative adhesions, incisional hernias (which may require surgical correction) and wound infections.[20] If a caesarean is performed in an emergency, the risk of the surgery may be increased due to a number of factors. The patient's stomach may not be empty, increasing the risk of anaesthesia.[21] Other risks include severe blood loss (which may require a blood transfusion) and postdural-puncture spinal headaches.[20]

text: Wound infections occur after caesarean sections at a rate of 3-15%.[22]

text: Women who had caesarean sections are more likely to have problems with later pregnancies, and it is recommended that women who want larger families should not seek an elective caesarean unless there are medical indications to do so. The risk of placenta accreta, a potentially life-threatening condition which is more likely to develop where a woman has had a previous caesarean section, is 0.13% after two caesarean sections, but increases to 2.13% after four and then to 6.74% after six or more. Along with this is a similar rise in the risk of emergency hysterectomies at delivery.[23]

text: Mothers can experience increased incidence of postnatal depression, and can experience significant psychological trauma and ongoing birth-related post-traumatic stress disorder after obstetric intervention during the birthing process.[24] Factors like pain in first stage of labor, feelings of powerlessness, intrusive emergency obstetric intervention are important in the subsequent development of psychological issues related to labour and delivery.[24]

text: Subsequent pregnancies[edit]

text: Women who have had a caesarean for any reason are somewhat less likely to become pregnant again as compared to women who have previously delivered only vaginally, but the effect is small.[25]

text: Women who had just one previous caesarean section are more likely to have problems with their second birth.[3] Delivery after previous Caesarean section is by either of two main options:

text:
Vaginal birth after Caesarean section (VBAC)
Elective repeat Caesarean section (ERCS)

text: Both have higher risks than a vaginal birth with no previous caesarean section. There are many issues which must be taken into account when planning the mode of delivery for every pregnancy, not just those complicated by a previous caesarean section and there is a list of some of these issues in the list of indications for section in the first part of this article. A vaginal birth after caesarean section (VBAC) confers a higher risk of uterine rupture (5 per 1,000), blood transfusion or endometritis (10 per 1,000), and perinatal death of the child (0.25 per 1,000).[26] Furthermore, 20% to 40% of planned VBAC attempts end in caesarean section being needed, with greater risks of complications in an emergency repeat caesarean section than in an elective repeat caesarean section.[27][28] On the other hand, VBAC confers less maternal morbidity and a decreased risk of complications in future pregnancies than elective repeat caesarean section.[29]

text: Adhesions[edit]

text: There are number of steps that can be taken during abdominal or pelvic surgery to minimize postoperative complications, such as the formation of adhesions. Such techniques and principles may include:

text: However, despite these proactive measures, adhesion formation is a recognized complication of any abdominal or pelvic surgery. To prevent adhesions from forming after caesarean section, adhesion barrier can be put during surgery to minimize the risk of adhesions between the uterus and ovaries, the small bowel, and almost any tissue in the abdomen or pelvis. This is not current UK practice though as there is no compelling evidence to support the benefit of this intervention.

text: Adhesions can cause long term problems, such as:

text: The risk of adhesion formation is one reason why vaginal delivery is usually considered safer than elective caesarean section where there is no medical indication for section for either maternal or fetal reasons.

text: Child[edit]

text: Non-medically indicated (elective) childbirth before 39 weeks gestation "carry significant risks for the baby with no known benefit to the mother." Complications from elective caesarean before 39 weeks include: newborn mortality at 37 weeks may be up to 3 times the number at 40 weeks, and was elevated compared to 38 weeks gestation. These “early term” births were associated with more death during infancy, compared to those occurring at 39 to 41 weeks ("full term").[30] Researchers in one study and another review found many benefits to going full term, but “no adverse effects” in the health of the mothers or babies.[30][31]

text: The American Congress of Obstetricians and Gynecologists and medical policy makers review research studies and find more incidence of suspected or proven sepsis, RDS, hypoglycemia, need for respiratory support, need for NICU admission, and need for hospitalization > 4–5 days. In the case of caesarean sections, rates of respiratory death were 14 times higher in pre-labor at 37 compared with 40 weeks gestation, and 8.2 times higher for pre-labor caesarean at 38 weeks. In this review, no studies found decreased neonatal morbidity due to non-medically indicated (elective) delivery before 39 weeks.[30]

text: For otherwise healthy twin pregnancies where both twins are head down a trial of vaginal delivery is recommended at between 37 and 38 weeks.[10][32] Vaginal delivery in this case does not worsen the outcome for either infant as compared with caesarean section.[32] There is some controversy on the best method of delivery where the first twin is head first and the second is not, but most obstetricians will recommend normal delivery unless there are other reasons to avoid vaginal birth.[32] When the first twin is not head down, a caesarean section is often recommended.[32] Regardless of whether the twins are delivered by section or vaginally, the medical literature recommends delivery of dichorionic twins at 38 weeks, and monochorionic twins (identical twins sharing a placenta) by 37 weeks due to the increased risk of stillbirth in monochorionic twins who remain in utero after 37 weeks.[33][34] The consensus is that late preterm delivery of monochorionic twins is justified because the risk of stillbirth for post-37 week delivery is significantly higher than the risks posed by delivering monochorionic twins near term (i.e., 36–37 weeks).[35] The consensus concerning monoamniotic twins (identical twins sharing an amniotic sac), the highest risk type of twins, is that they should be delivered by caesarean section at or shortly after 32 weeks, since the risks of intrauterine death of one or both twins is higher after this gestation than the risk of complications of prematurity.[36][37][38]

text: In a research study widely publicized, singleton children born earlier than 39 weeks may have developmental problems, including slower learning in reading and math.[39]

text: Other risks include:

text:
Wet lung: Retention of fluid in the lungs can occur if not expelled by the pressure of contractions during labor.[40]
Potential for early delivery and complications: Preterm delivery may be inadvertently carried out if due-date calculation is inaccurate. One study found an increased complication risk if a repeat elective caesarean section is performed even a few days before the recommended 39 weeks.[41]
Higher infant mortality risk: In caesarean sections performed with no indicated medical risk (singleton at full term in a head-down position with no other obstetric or medical complications), the risk of death in the first 28 days of life has been cited as 1.77 per 1,000 live births among women who had caesarean sections, compared to 0.62 per 1,000 for women who delivered vaginally.[42]

text: Birth by caesarean section also seems to be associated with worse health outcomes later in life, including overweight or obesitas and problems in the immune system.[43]

text: Classification[edit]

text: Caesarean sections have been classified in various ways by different perspectives.[44] One way to discuss all classification systems is to group them by their focus either on the urgency of the procedure, characteristics of the mother, or as a group based on other, less commonly discussed factors.[44]

text: It is most common to classify caesarean sections by the urgency of performing them.[44]

text: By urgency[edit]

text: Conventionally, caesarean sections are classified as being either an elective surgery or an emergency operation.[45] Classification is used to help communication between the obstetric, midwifery and anaesthetic team for discussion of the most appropriate method of anaesthesia. The decision whether to perform general anesthesia or regional anesthesia (spinal or epidural anaesthetic) is important and is based on many indications, including how urgent the delivery needs to be as well as the medical and obstetric history of the woman.[45] Regional anaesthetic is almost always safer for the woman and the baby but sometimes general anaesthetic is safer for one or both, and the classification of urgency of the delivery is an important issue affecting this decision.

text: A planned caesarean (or elective/scheduled caesarean), arranged ahead of time, is most commonly arranged for medical indications which have developed before or during the pregnancy, and ideally after 39 weeks of gestation.[citation needed] In the UK, this is classified as a 'grade 4' section (delivery timed to suit the needs of the service) since the need for delivery is not urgent. Emergency caesarean sections are performed in pregnancies in which a vaginal delivery was planned initially, but an indication for caesarean delivery has since developed. In the UK they are further classified as grade 3 (delivery within 4 hours of the decision, no maternal or fetal compromise), grade 2 (delivery required within 90 minutes of the decision but no immediate threat to the life of the woman or the fetus) or grade 1 (delivery required within 30 minutes of the decision: immediate threat to the life of the mother or the baby or both.)

text: Elective caesarean sections may be performed on the basis of an obstetrical or medical indication, or because of a medically non-indicated maternal request.[10] Among women in the United Kingdom, Sweden and Australia, about 7% preferred caesarean section as a method of delivery.[10] In cases without medical indications the American Congress of Obstetricians and Gynecologists and the UK Royal College of Obstetricians and Gynaecologists recommend a planned vaginal delivery.[46] The National Institute for Health and Care Excellence recommends that if after a women has been provided information on the risk of a planned caesarean section and she still insists on the procedure it should be provided.[10] If provided this should be done at 39 weeks of gestation or later.[46]

text: By characteristics of the mother[edit]

text: Caesarean delivery on maternal request[edit]

text: Caesarean delivery on maternal request (CDMR) is a medically unnecessary caesarean section, where the conduct of a childbirth via a caesarean section is requested by the pregnant patient even though there is not a medical indication to have the surgery.[47]

text: After previous Caesarean[edit]

text: Mothers who have previously had a caesarean section are more likely to have a caesarean section for future pregnancies than mothers who have never had a caesarean section. There is discussion about the circumstances under which women should have a vaginal birth after a previous caesarean.

text: Vaginal birth after caesarean (VBAC) is the practice of birthing a baby vaginally after a previous baby has been delivered by caesarean section (surgically).[48] According to The American Congress of Obstetricians and Gynecologists (ACOG), successful VBAC is associated with decreased maternal morbidity and a decreased risk of complications in future pregnancies.[49] According to the American Pregnancy Association, 90% of women who have undergone caesarean deliveries are candidates for VBAC.[27] Approximately 60-80% of women opting for VBAC will successfully give birth vaginally, which is comparable to the overall vaginal delivery rate in the United States in 2010.[27][28][50]

text: Twins[edit]

text: For otherwise healthy twin pregnancies where both twins are head down a trial of vaginal delivery is recommended at between 37 and 38 weeks.[10][32] Vaginal delivery in this case does not worsen the outcome for either infant as compared with caesarean section.[32] There is controversy on the best method of delivery where the first twin is head first and the second is not.[32] When the first twin is not head down at the point of labour starting, a caesarean section should be recommended.[32] Although the second twin typically has a higher frequency of problems, it is not known if a planned caesarean section affects this.[10] It is estimated that 75% of twin pregnancies in the United States were delivered by caesarean section in 2008.[51]

text: Breech birth[edit]

text: A breech birth is the birth of a baby from a breech presentation, in which the baby exits the pelvis with the buttocks or feet first as opposed to the normal head-first presentation. In breech presentation, fetal heart sounds are heard just above the umbilicus.

text: The bottom-down position presents some hazards to the baby during the process of birth, and the mode of delivery (vaginal versus caesarean) is controversial in the fields of obstetrics and midwifery.

text: Though vaginal birth is possible for the breech baby, certain fetal and maternal factors influence the safety of vaginal breech birth. The majority of breech babies born in the United States and the UK are delivered by caesarean section as studies have shown increased risks of morbidity and mortality for vaginal breech delivery, and most obstetricians counsel against planned vaginal breech birth for this reason. As a result of reduced numbers of actual vaginal breech deliveries, obstetricians and midwives are at risk of de-skilling in this important skill. All those involved in delivery of obstetric and midwifery care in the UK undergo mandatory training in conducting breech deliveries in the simulation environment (using dummy pelvises and mannequins to allow practice of this important skill) and this training is carried out regularly to keep skills up to date.

text: Resuscitative hysterotomy[edit]

text: A resuscitative hysterotomy, also known as a peri-mortem caesarean delivery, is an emergency caesarean delivery carried out where maternal cardiac arrest has occurred, to assist in resuscitation of the mother by removing the aortocaval compression generated by the gravid uterus. Unlike other forms of caesarean section, the welfare of the fetus is a secondary priority only, and the procedure may be performed even prior to the limit of fetal viability if it is judged to be of benefit to the mother.

text: Other ways, including by surgery technique[edit]

text: There are several types of caesarean section (CS). An important distinction lies in the type of incision (longitudinal or transverse) made on the uterus, apart from the incision on the skin: the vast majority of skin incisions are a transverse suprapubic approach known as a Pfannenstiel incision but there is no way of knowing from the skin scar which way the uterine incision was conducted.

text:
The classical caesarean section involves a midline incision on the uterus longitudinal incision which allows a larger space to deliver the baby. It is performed at very early gestations where the lower segment of the uterus is unformed as it is safer in this situation for the baby: but it is rarely performed other than at these early gestations, as the operation is more prone to complications than a low transverse uterine incision. Any woman who has had a classical section will be recommended to have an elective repeat section in subsequent pregnancies as the vertical incision is much more likely to rupture in labour than the transverse incision.
The lower uterine segment section is the procedure most commonly used today; it involves a transverse cut just above the edge of the bladder. It results in less blood loss and has fewer early and late complications for the mother, as well as allowing her to consider a vaginal birth in the next pregnancy.
A caesarean hysterectomy consists of a caesarean section followed by the removal of the uterus. This may be done in cases of intractable bleeding or when the placenta cannot be separated from the uterus.

text: The EXIT procedure is a specialized surgical delivery procedure used to deliver babies who have airway compression.

text: The Misgav Ladach method is a modified caesarean section which has been used nearly all over the world since the 1990s. It was described by Michael Stark, the president of the New European Surgical Academy, at the time he was the director of Misgav Ladach, a general hospital in Jerusalem. The method was presented during a FIGO conference in Montréal in 1994[52] and then distributed by the University of Uppsala, Sweden, in more than 100 countries. This method is based on minimalistic principles. He examined all steps in caesarean sections in use, analyzed them for their necessity and, if found necessary, for their optimal way of performance. For the abdominal incision he used the modified Joel Cohen incision and compared the longitudinal abdominal structures to strings on musical instruments. As blood vessels and muscles have lateral sway, it is possible to stretch rather than cut them. The peritoneum is opened by repeat stretching, no abdominal swabs are used, the uterus is closed in one layer with a big needle to reduce the amount of foreign body as much as possible, the peritoneal layers remain unsutured and the abdomen is closed with two layers only. Women undergoing this operation recover quickly and can look after the newborns soon after surgery. There are many publications showing the advantages over traditional caesarean section methods. However, there is an increased risk of abruptio placentae and uterine rupture in subsequent pregnancies for women who underwent this method in prior deliveries.[53][54]

text: Technique[edit]

text: Antibiotic prophylaxis is used before an incision.[55] The uterus is incised, and this incision is extended with blunt pressure along a cephalad-caudad axis.[55] The infant is delivered, and the placenta is then removed.[55] The surgeon then makes a decision about uterine exteriorization.[55] Single-layer uterine closure is used when the mother does not want a future pregnancy.[55] When subcutaneous tissue is 2 cm thick or more, surgical suture is used.[55] Discouraged practices include manual cervical dilation, any subcutaneous drain, or supplemental oxygen therapy with intent to prevent infection.[55]

text: Caesarean section can be performed with single or double layer suturing of the uterine incision.[56] Single layer closure compared with double layer closure has been observed to result in reduced blood loss during the surgery. It is uncertain whether this is the direct effect of the suturing technique or if other factors such as the type and site of abdominal incision contribute to reduced blood loss.[57] Standard procedure includes the closure of the peritoneum. However, research questions this may not be needed, with some studies indicating peritoneal closure is associated with longer operative time and hospital stay.[58] The Misgave Ladach method is a surgery technical that may have fewer secondary complications and faster healing, due to the insertion into the muscle.[59]

text: In many hospitals the mother's partner is encouraged to attend the surgery to support the mother and share the experience. The anaesthetist will usually lower the drape temporarily as the child is delivered so the parents can see their newborn.[citation needed]

text: Anaesthesia[edit]

text: Both general and regional anaesthesia (spinal, epidural or combined spinal and epidural anaesthesia) are acceptable for use during Caesarean section. Evidence does not show a difference between regional anaesthesia and general anaesthesia with respect to major outcomes in the mother or baby.[60] Regional anaesthesia may be preferred as it allows the mother to be awake and interact immediately with her baby.[61] Other advantages of regional anesthesia may include the absence of typical risks of general anesthesia: pulmonary aspiration (which has a relatively high incidence in patients undergoing anesthesia in late pregnancy) of gastric contents and esophageal intubation.[60] However, one trial found no difference in satisfaction when general anaesthesia was compared with either spinal anaesthesia.[60]

text: Regional anaesthesia is used in 95% of deliveries, with spinal and combined spinal and epidural anaesthesia being the most commonly used regional techniques in scheduled Caesarean section.[62] Regional anaesthesia during Caesarean section is different from the analgesia (pain relief) used in labor and vaginal delivery. The pain that is experienced because of surgery is greater than that of labor and therefore requires a more intense nerve block.

text: General anesthesia may be necessary because of specific risks to mother or child. Patients with heavy, uncontrolled bleeding may not tolerate the hemodynamic effects of regional anesthesia. General anesthesia is also preferred in very urgent cases, such as severe fetal distress, when there is no time to perform a regional anesthesia.

text: Prevention of complications[edit]

text: Postpartum infection is one of the main causes of maternal death and may account for 0% of maternal deaths globally.[63][10][64] Caesarean section greatly increases the risk of infection and associated morbidity (estimated to be between 5 and 20 times as high), and routine use of antibiotic prophylaxis to prevent infections is recommended.[64] Infection can occur in around 8% of women who have caesareans,[10] largely endometritis, urinary tract infections and wound infections. The use of preventative antibiotics in women undergoing cesarean section decreased wound infection, endometritis, and serious infectious complications by about 65%.[64] Side effects and effect on the baby is unclear.[64]

text: Women who have caesareans can recognize the signs of fever that indicate the possibility of wound infection.[10] Taking antibiotics before skin incision rather than after cord clamping reduces the risk for the mother, without increasing adverse effects for the baby.[10][65] Whether a particular type of skin cleaner improves outcomes is unclear.[66]

text: Some doctors believe that during a caesarean section, mechanical cervical dilation with a finger or forceps will prevent the obstruction of blood and lochia drainage, and thereby benefit the mother by reducing risk of death.[67] The available clinical evidence is not sufficient to draw a conclusion on the effect of this practice.[67]

text: Recovery[edit]

text: It is common for women who undergo caesarian section to have reduced or absent bowel movements for hours to days. During this time, women may experience abdominal cramps, nausea and vomiting.This usually resolves without treatment.[68] Abdominal, wound and back pain can continue for months after a caesarean section. Non-steroidal anti-inflammatory drugs can be helpful.[10] Women who have had a caesarean are more likely to experience pain that interferes with their usual activities than women who have vaginal births, although by six months there is generally no longer a difference.[69] However, pain during sexual intercourse is less likely than after vaginal birth, although again, by six months there is no difference.[10]

text: There may be a somewhat higher incidence of postnatal depression in the first weeks after childbirth for women who have caesarean sections, but this difference does not persist.[10] Some women who have had caesarean sections, especially emergency caesareans, experience post-traumatic stress disorder.[10]

text: Usage[edit]

text: In Italy the incidence of Caesarean sections is particularly high, although it varies from region to region.[70] In Campania, 60% of 2008 births reportedly occurred via Caesarean sections.[71] In the Rome region, the mean incidence is around 44%, but can reach as high as 85% in some private clinics.[72][73]

text: With nearly 1.3 million stays, Caesarean section was one of the most common procedures performed in U.S. hospitals in 2011. It was the second-most common procedure performed for people ages 18 to 44 years old.[74] Caesarean rates in the U.S. have risen considerably since 1996.[75] The procedure increased 60% from 1996 to 2009. In 2010, the Caesarean delivery rate was 32.8% of all births (a slight decrease from 2009's high of 32.9% of all births).[76] A study found that in 2011, women covered by private insurance were 11% more likely to have a caesarean section delivery than those covered by Medicaid.[77]

text: China has been cited as having the highest rates of C-sections in the world at 46% as of 2008.[78]

text: Studies have shown that continuity of care with a known carer may significantly decrease the rate of Caesarean delivery[79] but there is also research that appears to show that there is no significant difference in Caesarean rates when comparing midwife continuity care to conventional fragmented care.[80]

text: More emergency Caesareans—about 66%—are performed during the day rather than during the night.[81]

text: The rate has risen to 46% in China and to levels of 25% and above in many Asian, European and Latin American countries.[82] The rate has increased in the United States, to 33% of all births in 2012, up from 21% in 1996.[3] Across Europe, there are differences between countries: in Italy the Caesarean section rate is 40%, while in the Nordic countries it is 14%.[83]

text: Increasing use[edit]

text: In the United States C-section rates have increased from just over 20% in 1996 to 33% in 2011.[3] This increase has not resulted in improved outcomes resulting in the position that C-sections may be done too frequently.[3]

text: The World Health Organization officially withdrew its previous recommendation of a 15% C-section rate in June 2010. Their official statement read, "There is no empirical evidence for an optimum percentage. What matters most is that all women who need caesarean sections receive them."[84]

text: The US National Institutes of Health says rises in rates of Caesarean sections are not, in isolation, a cause for concern, but may reflect changing reproductive patterns: "The World Health Organization has determined an “ideal rate” of all caesarean deliveries (such as 15 percent) for a population.[47]

text: Speculation explaining a relationship between birth weight and maternal pelvis size has been proposed. The explanation, based on Darwinian-inspired logic, states that since the advent of successful Caesarean birth more mothers with small pelvises and babies with large birth weights survive. This hypothesis would predict an increased average birth weight, which has been observed. It is unclear what component contributes more to this effect; evolution or environment.[85]

text: Epidemiology[edit]

text: Global rates of caesarean section rates are increasing.[22] In the United Kingdom, in 2008, the Caesarean section rate was 24%.[86] In Ireland the rate was 26.1% in 2009.[87] The Canadian rate was 26% in 2005–2006.[88] Australia has a high Caesarean section rate, at 31% in 2007.[89] In the United States the rate of C-section is around 33% and varies from 23% to 40% depending on the state in question.[3]One out three women who gave birth in the US delivered by cesarean in 2011. In 2012, close to 23 million C-sections were done globally in 2012.[8] At one time the rate of 10% and 15% was thought to be ideal.[4] A higher rate of 19% may result in better outcomes.[8] More than 50 nations have rates greater than 27%. Another 45 countries have rates less than 7.5%[8] There are efforts to both improve access to and reduce the use of C-section.[8] In the United States about 33% of deliveries are by C-section.[2][3] The rates in the UK and Australia are 26.5% and 32.3% respectively. In China, the most recent CS rate reported was 41%.[22] Globally, 1% of all cesarean deliveries are done without the medical need for one. Overall, the rate of caesarean section rate was 25.7% during 2004-2008.[90][91]

text: Wound infections occur after cesarean sections at a rate of 3-15%.[22] Some women are at greater risk for developing a surgical site infection after delivery. The presence of choriamnionitis and obesity predisposes the woman to developing a surgical site infection.[22]

text: History[edit]

text: The mother of Bindusara (born c. 320 BC, ruled 298 – c. 272 BC), the second Mauryan Samrat (emperor) of India, accidentally consumed poison and died when she was close to delivering him. Chanakya, the Chandragupta's teacher and adviser, made up his mind that the baby should survive. He cut open the belly of the queen and took out the baby, thus saving the baby's life.[92][93]

text: According to the ancient Chinese Records of the Grand Historian, Luzhong, a sixth-generation descendant of the Yellow Emperor, had six sons, all born by "cutting open the body". The sixth son Jilian founded the House of Mi that ruled the State of Chu (c. 1030–223 BC).[94]

text: In the Irish mythological text the Ulster Cycle, the character Furbaide Ferbend is said to have been born by posthumous caesarean section, after his mother was murdered by his evil aunt Medb.

text: The Babylonian Talmud, an ancient Jewish religious text, mentions a procedure similar to the caesarean section. The procedure is termed yotzei dofen. It also discusses at length the permissibility of performing a c-section on a dying or dead mother. [93]

text: Pliny the Elder theorized that Julius Caesar's name came from an ancestor who was born by caesarean section, but the truth of this is debated (see the discussion of the etymology of Caesar). The Ancient Roman caesarean section was first performed to remove a baby from the womb of a mother who died during childbirth. Julius Caesar's mother, Aurelia, lived through childbirth and successfully gave birth to her son, ruling out the possibility the Roman ruler and general was born by caesarean section. His first wife however died in childbirth, giving birth to a stilborn son who might have lived had a caesarean taken place.

text: The Catalan saint Raymond Nonnatus (1204–1240), received his surname—from the Latin non-natus ("not born")—because he was born by caesarean section. His mother died while giving birth to him.[95]

text: An early account of caesarean section in Iran is mentioned in the book of Shahnameh, written around 1000 AD, and relates to the birth of Rostam, the national legendary hero of Iran.[96][97] According to the Shahnameh, the Simurgh instructed Zal upon how to perform a Caesarean section, thus saving Rudaba and the child Rostam.[98]

text: Caesarean section usually resulted in the death of the mother. In an account from the 1580s, in Siegershausen, Switzerland, Jakob Nufer a pig gelder, is supposed to have performed the operation on his wife after a prolonged labour.[99] However, there is also some basis for supposing that Jewish women regularly survived the operation in Roman times.[100] For most of the time since the 16th century, the procedure had a high mortality rate. However, it was long considered an extreme measure, performed only when the mother was already dead or considered to be beyond help. In Great Britain and Ireland, the mortality rate in 1865 was 85%. Key steps in reducing mortality were:

text:
Introduction of the transverse incision technique to minimize bleeding by Ferdinand Adolf Kehrer in 1881 is thought to be first modern CS performed.
The introduction of uterine suturing by Max Sänger in 1882
Modification by Hermann Johannes Pfannenstiel in 1900, see Pfannenstiel incision
Extraperitoneal CS and then moving to low transverse incision (Krönig, 1912)[clarification needed]
Adherence to principles of asepsis
Anesthesia advances
Blood transfusion
Antibiotics

text: European travelers in the Great Lakes region of Africa during the 19th century observed Caesarean sections being performed on a regular basis.[101] The expectant mother was normally anesthetized with alcohol, and herbal mixtures were used to encourage healing. From the well-developed nature of the procedures employed, European observers concluded they had been employed for some time.[101] James Barry carried out the first successful Caesarean by a European doctor in Africa in Cape Town, while posted there between 1817 and 1828.[102]

text: The first successful Caesarean section to be performed in America took place in Mason County, Virginia (now Mason County, West Virginia), in 1794. The procedure was performed by Dr. Jesse Bennett on his wife Elizabeth.[103]

text: On March 5, 2000, in Mexico, Inés Ramírez performed a Caesarean section on herself and survived, as did her son, Orlando Ruiz Ramírez.[104]

text: Caesarius of Terracina[edit]

text: The patron saint of Caesarean section is Caesarius of Africa, a young deacon martyred at Terracina, who has replaced and Christianized the pagan figure of Caesar.[105] The martyr (Saint Cesareo, in italian) is invoked for the good success of this surgical procedure.

text: Society and culture[edit]

text: Etymology[edit]

text: The Roman Lex Regia (royal law), later the Lex Caesarea (imperial law), of Numa Pompilius (715–673 BC),[106] required the child of a mother dead in childbirth to be cut from her womb.[107] There was a cultural taboo that mothers not be buried pregnant,[108] that may have reflected a way of saving some fetuses. Roman practice requiring a living mother to be in her tenth month of pregnancy before resorting to the procedure, reflecting the knowledge that she could not survive the delivery.[109] Speculation that the Roman dictator Julius Caesar was born by the method now known as C-section is apparently false.[110] Although Caesarean sections were performed in Roman times, no classical source records a mother surviving such a delivery.[107][111] As late as the 12th century, scholar and physician Maimonides expresses doubt over the possibility of a woman's surviving this procedure and again falling pregnant.[112] The term has also been explained as deriving from the verb caedere, "to cut", with children delivered this way referred to as caesones. Pliny the Elder refers to a certain Julius Caesar (an ancestor of the famous Roman statesman) as ab utero caeso, "cut from the womb" giving this as an explanation for the cognomen "Caesar" which was then carried by his descendants.[107] Nonetheless, even if the etymological hypothesis linking the caesarean section to Julius Caesar is a false etymology, it has been widely believed. For example, the Oxford English Dictionary defines Caesarean birth as "the delivery of a child by cutting through the walls of the abdomen when delivery cannot take place in the natural way, as was done in the case of Julius Caesar".[113] Merriam-Webster's Collegiate Dictionary (11th edition) leaves room for etymological uncertainty with the phrase, "from the legendary association of such a delivery with the Roman cognomen Caesar"[114]

text: Some link with Julius Caesar or with Roman emperors exists in other languages as well. For example, the modern German, Norwegian, Danish, Dutch, Swedish, Turkish and Hungarian terms are respectively Kaiserschnitt, keisersnitt, kejsersnit, keizersnede, kejsarsnitt, sezaryen and császármetszés (literally: "emperor's cut").[115] The German term has also been imported into Japanese (帝王切開 teiōsekkai) and Korean (제왕 절개 jewang jeolgae), both literally meaning "emperor incision". Similarly, in western Slavic (Polish) cięcie cesarskie, (Czech) císařský řez and (Slovak) cisársky rez means "emperor's cut", whereas the south Slavic term is Serbian царски рез and Slovenian cárski réz, literally tzar's cut. The Russian term kesarevo secheniye (Кесарево сечение késarevo sečénije) literally means Caesar's section. The Arabic term (ولادة قيصرية wilaada qaySaríyya) also means "Caesarean birth." The Hebrew term ניתוח קיסרי (nitúakh Keisári) translates literally as Caesarean surgery. In Romania and Portugal,[116] it is usually called cesariana, meaning from (or related to) Caesar.[citation needed]

text: According to Shahnameh ancient Persian book, the hero Rostam was the first person who was born with this method and term رستمينه (rostamineh) is corresponded to Caesarean.[citation needed] Also, Hindu mythical monkey god Hanuman was born through a similar procedure on his mother Anjani.

text: Finally, the Roman praenomen (given name) Caeso was said to be given to children who were born via C-section. While this was probably just folk etymology made popular by Pliny the Elder, it was well known by the time the term came into common use.[117]

text: Spelling[edit]

text: The term "caesarean" is spelled in various accepted ways, as discussed at Wiktionary. The Medical Subject Headings (MeSH) of the United States National Library of Medicine (NLM) uses "cesarean section".

text: Special cases[edit]

text: In Judaism there is a dispute among the poskim (Rabbinic authorities) as to whether a first-born son from a Caesarean section has the laws of a bechor.[118] Traditionally, a male child delivered by Caesarean is not eligible for the Pidyon HaBen dedication ritual.[119][120]

text: In rare cases, caesarean sections can be used to remove a dead fetus. A late-term abortion using Caesarean section procedures is termed a hysterotomy abortion and is very rarely performed.[121]

text: Self-inflicted caesarean section is the concept of a mother alone performing her own caesarean section. There have apparently been a few successful cases, notably Inés Ramírez Pérez of Mexico who in March 2000, performed a successful Caesarean section on herself.[122][123][124]