Braxton Hicks contractions, also known as false labour (British English, false labor in American English) or practice contractions. Braxton Hicks are sporadic uterine contractions that actually start at about 6 weeks, although one will not feel them that early. Most women start feeling them during the second or third trimester of pregnancy. Braxton Hicks contractions are a tightening of the uterine muscles for one to two minutes and is thought to be an aid to the body in its preparation for birth. Not all expectant mothers have these contractions. They are thought to be part of the process of effacement, the thinning and dilation of the cervix.