Effacement and dilatation of the cervix before birth

Watercolour showing effacement and dilation of the cervix. Effacement, or shortening and thinning of the cervix, usually starts within the last month of a first pregnancy due to Braxton Hicks contractions. The process is completed during the first stage of labour. With the aid of strong uterine contractions the membranes usually rupture and the cervix dilates to 10cm, which marks the end of the first stage. In subsequent pregnancies, effacement and dilatation of the cervix occur simultaneously.