American Medical Association Family Medical Guide - American Medical Association [297]
Stages of Labor
Labor can be divided into three general stages. In the first stage, contractions of the muscles of the uterus open the cervix to allow the baby to pass into the vagina. In the second stage, the baby moves through and then out of the vagina (delivery), aided by contractions and some pushing by the mother. In the third stage, the placenta is expelled from the uterus.
First Stage: Dilation and Effacement
The first stage of labor begins with the first contractions, which help widen (dilate) the cervix. With each contraction, the cervix dilates and becomes thinner, or effaced. Effacement is given in percentages, with 100 percent effacement indicating that the cervix is ready for delivery. Dilation is measured in centimeters, with a diameter of 10 centimeters (about 4 inches) indicating full dilation. At full dilation, contractions are intense and occur 2 to 3 minutes apart. This is called the transition phase, and it is the most difficult, painful stage. By the end of this stage, the baby has begun to enter the vagina, and the mother may feel a strong urge to push.
The average duration of the first stage of labor is 12 hours for a first baby and 4 to 8 hours for a subsequent delivery. For some women who are having their first baby, the first stage can last longer than 24 hours. For women who have had several babies, this stage may last only a few minutes.
Second Stage: Delivery
During the second stage, contractions move the baby down the birth canal with the help of the mother’s pushing, or bearing down. You will be told to push only when you are having a contraction, because the contractions double the effect of your pushing, allowing you to rest between contractions, which helps you conserve energy. An episiotomy (see page 533) may be performed toward the end of the second stage of labor, before the baby’s head emerges.
The second stage of labor ends when the baby is completely out of the vagina. Immediately after birth, the umbilical cord (which has connected the baby to the placenta) is tied and cut. The second stage can last up to 3 hours for a first baby and 2 hours for a subsequent delivery.
Labor and delivery
During the first stage of labor, uterine contractions increase in strength and frequency and move the baby down into the birth canal (top). When the cervix is fully dilated, the contractions become stronger, pushing the baby farther down the birth canal and out of the vagina (bottom).
Third Stage: Expelling the Placenta
In the third stage of labor, after delivery of the baby, the placenta detaches from the uterine wall and is expelled from the uterus (afterbirth). Contractions (usually less painful than those of labor) help the uterus expel the placenta. Doctors often assist the delivery of the placenta by massaging the woman’s abdomen and pulling gently on the umbilical cord during contractions.
The third stage can last from a few minutes to half an hour. After the placenta has been expelled, the mother may be given medication to prevent excessive bleeding. The doctor cleans and stitches any incisions from the episiotomy (see next page) or tears in the vagina.
Pain Relief During Labor and Delivery
The intensity of pain during labor varies significantly from woman to woman and is partly influenced by a woman’s expectations. If you are frightened or tense, you may feel pain more acutely. If you attended childbirth classes with your labor coach, you will know what to expect and probably will be better prepared to deal with the pain. You can help ease contractions by staying upright and active as long as possible (without tiring yourself out); in addition, gravity helps the baby descend and speeds up dilation of the cervix. Breathe slowly and deeply during and after each contraction. Try a variety of positions to find the ones that are most comfortable.
You may not need pain relief during labor but, if you do,