Active Phase

The cervix dilates from about 4 centimeters to the full 10 centimeters. It thins and pulls back (effaces) until it merges with the rest of the uterus.

The presenting part of the baby (the part of the baby that will deliver first), usually the head, begins to descend into a woman’s pelvis.

A woman begins to feel the urge to push as the baby descends, but she should resist it until the cervix is fully dilated. Pushing too early may be unnecessarily tiring and may tear the cervix.

This phase averages about 5 to 7 hours in a first pregnancy and 2 to 4 hours in subsequent pregnancies.