Why does a female's cervix dilate prior to delivering a baby?

Effacement: The cervix - which is normally long and thick, measuring about 1-2 inches, starts to get shorter and thinner. This process is known as effacement. As the cervix gets more and more effaced, it gets shorter and shorter and "pulled up" into the lower part of the uterus.

Dilation: At the same time, the cervix softens and begins to open up - known as dilation. This widening, allows a smooth passage for the baby’s head and the rest of the body from the uterus into the vaginal canal.