At the end of pregnancy, when the baby drops down into the pelvis, the baby’s head puts pressure
on the cervix. This constant pressure causes
your body to release oxytocin, which is the hormone that causes contractions.
The contractions push the baby even farther down onto the cervix, which causes it to dilate, which causes more contractions and so on…. It’s the combination of hormones and pressure from the baby’s head that cause cervix dilation.