Braxton Hicks contractions or “false” labor pain occur during pregnancy, often before the beginning of the actual labor , due to occasional tightening and relaxing of the uterus. English physician John Braxton Hicks was the first person to describe them in 1872 . Although, not all women get Braxton Hicks contractions during pregnancy, they are perfectly normal, and not something to worry about.
The contractions do not generally begin before the third trimester (pregnancy week 28 to week 40). However, one may start feeling mild to moderate false contractions as early as the second trimester (pregnancy week 13 to week 27). 
They are usually not painful but may lead to certain uncomfortable signs and symptoms. Most women complain of tightness in the lower abdomen which causes shortness of breath. They may be similar to normal menstrual cramps in some women. 
Some women may find it difficult to determine whether they are having Braxton Hicks contractions or is it just their babies moving (kicking or baling up) within the uterus. The basic difference between the two is that unlike the baby movements, which is quite isolated, the Braxton Hick contractions continue for a few seconds at a time.
Keeping the uterus muscle fibers well-toned for the real contractions and delivery  is often believed to be one of the main causes of the contractions.
Although, they are not known to contribute to the actual dilation of the cervix,  some experts believe them to play a significant role for preparing the cervix for childbirth (the cervix becomes shorter and stretchier before deliver). However according to others, the contractions cannot possibly affect the cervix as the cervical changes do not occur until a woman goes into labor, by which point she starts feeling real contractions.
It might be difficult to differentiate Braxton Hicks contractions from real contractions (occurring due to the release of oxytocin hormone) , especially if they lead to symptoms like abdominal tightness during the later weeks of pregnancy. The duration, frequency and severity of the pain help with the differentiation:
|Braxton Hicks Contractions||Labor Contractions|
|Infrequent in nature, occurs every 5 to 10 minutes a few times a day||Occurs more regularly, usually 2 to 3 minutes apart |
|Not constant, does not last longer than a few seconds||Each one tends to last for 30 to 90 seconds |
|Severity depends on activity levels as the contractions stop when one changes walks, sits down or changes position||Remains consistent regardless of one’s activity level and position|
|Usually quite weak or strong in the beginning, getting weaker with time ||Causes a sharp pain|
|Felt primarily in the lower abdomen (sometimes in the upper abdomen)||May begin in the abdomen, moving toward the lower back or vice versa |
Contractions associated with pre-term labor are sometimes mistaken for Braxton Hicks contractions, although they are much more intense. Pre-term labor requires immediate medical attention;  otherwise, it can lead to various dangerous pregnancy and birth related complications. One should look for the following signs to determine whether it is time to call the doctor:
Its ICD-9 code is 644.1 while the ICD-10 code is O47.