What Happens During a Human Birth?

During labor, a woman's cervix slowly widens, known as dilation, and contractions occur every five to 20 minutes, lasting about 60 seconds, the March of Dimes Foundation states. The length, intensity and frequency of the contractions increase, the cervix reaches full dilation at 10 centimeters, and the woman's water breaks naturally or manually. At this point, a woman typically has medical attention and pushes to help the baby exit the birth canal through the expanded cervical opening.

The first stage of childbirth is divided into early labor and active labor, according to Mayo Clinic. While the overall length of labor and delivery differs for every pregnancy, early labor is generally the longest period when the cervix first begins dilation, and contractions are short. The cervical lining also thins out, known as effacement, and the mucus plug that closes off the cervix is eventually ejected from the vagina as a brown or bloody discharge.

A woman usually becomes less comfortable during active labor as pressure builds in her back and contractions strengthen, Mayo Clinic states. She may have pain, leg cramps or nausea, but she should try to relax in soothing positions and breathe between contractions while waiting for full dilation. During the delivery stage, the medical team may tell the woman when and how intensely to push to prevent excessive stress on vaginal tissues. Once the baby's head exits the body, a doctor or nurse clears the child's airway and guides the rest of the body out.