Cervical effacement and dilatation in childbirth

Throughout pregnancy, the cervix is kept closed with the mucus plug in place to prevent the entry of exogenous agents or the early exit of the foetus. Mothers who have already given birth in previous deliveries may have a slightly more open cervix than those who are primigravid.

At the onset of labour, the cervix undergoes two important changes: effacement and dilatation. Effacement is the progressive shortening of the cervix as contractions increase. Once the cervix has been effaced, it begins to dilate to an opening of about 10 cm, which allows the baby to come out.