Braxton Hicks contractions are extremely common. In fact, all pregnant women experience these contractions, according to All About Women Obstetrics and Gynecology Center. Braxton Hicks contractions usually begin after the 20th week of pregnancy, although in second and third pregnancies, they could begin earlier. Not all expecting mothers feel these contractions when they occur.
Braxton Hicks contractions increase in strength from week 20 through week 32, right up until it's time for real labor to begin, according to What to Expect. The major differences between Braxton Hicks contractions and real ones are that Braxton Hicks are infrequent, irregular and not strong enough to actually push the baby out. They usually begin as a painless tightening or squeezing sensation that starts at the top of the uterine muscles and radiates downward. They cause the abdomen to become hard and contorted, and they usually last between 15 and 30 seconds.
According to Parents Magazine, Braxton Hicks contractions are named after the 19th century English doctor John Braxton Hicks, who discovered them. They are sometimes referred to as false labor or practice contractions, and indeed they are the body's way of practicing and preparing for true labor. Braxton Hicks help to thin and dilate the cervix, and they become more pronounced with each subsequent pregnancy.