Premature rupture of the membranes is the leaking of amniotic fluid from around the fetus before labor starts.
Usually, the fluid-filled membranes containing the fetus rupture during labor. But in about 10% of normal pregnancies, the membranes rupture before labor starts. The membranes may rupture near the due date (at 37 weeks or later, which is considered full term) or earlier (called preterm premature rupture if it occurs earlier than 37 weeks). If rupture is preterm, delivery is also likely to be too early (preterm). Regardless of when premature rupture occurs, it increases the risk of infection in the uterus and in the fetus. The fetus is also more likely to be in an abnormal position, and the placenta is more likely to detach too soon (placental abruption).
After the membranes rupture, contractions usually begin within 12 to 48 hours when the woman is near term but can take 4 days or longer if rupture occurs before 34 weeks of pregnancy. Rupture of the membranes is commonly described as “the water breaks.” The fluid within the membranes (amniotic fluid) then flows out from the vagina. The flow varies from a trickle to a gush. As soon as the membranes have ruptured, a woman should contact her doctor or midwife.
Using a speculum, the doctor or midwife examines the pelvis to confirm that the membranes have ruptured and to estimate how much the cervix (the lower part of the uterus) has opened (dilated).
If labor does not begin within 6 to 12 hours, the risk of infection in the uterus and in the fetus increases. Therefore, a doctor or certified nurse midwife usually artificially starts (induces) labor, depending on whether the fetus is mature enough for delivery. If the pregnancy is 34 weeks or more, the fetus is assumed to be mature enough. If the pregnancy is less than 34 weeks, testing is done to determine whether the fetus's lungs are mature enough. Testing may involve taking a sample of amniotic fluid, usually from the vagina, and analyzing it. If the lungs are mature enough, labor is induced and the baby is delivered. If they are not, the doctor usually does not induce labor.
If labor is delayed:
If the fetus's lungs are not mature enough, labor is delayed. The woman may be hospitalized so that she can be monitored closely. Her temperature and pulse rate are usually recorded at least 3 times daily. An increase in temperature or pulse rate may be an early sign of infection. If an infection develops, labor is promptly induced and the baby is delivered.
Antibiotics are begun when rupture has been confirmed. Usually, antibiotics (such as erythromycin, ampicillin, and amoxicillin) are given intravenously, then by mouth for several days. They prolong the pregnancy and reduce the risk of infection in the newborn.
If the membranes rupture before the 32nd week of pregnancy, corticosteroids are given to help the fetus's lungs mature.
Last full review/revision June 2013 by Julie S. Moldenhauer, MD