Preterm premature rupture of the membranes (PPROM) is a term used to denote spontaneous rupture of the fetal membranes before the onset of labor (premature) and prior to term (preterm). Known risk factors for preterm rupture of the membranes include preceding preterm birth, occult amnionic fluid infection, multiple fetuses, and abruptio placentae.
At admission, 75 percent of women with PPROM are already in labor, 5 percent are delivered for other complications, and another 10 percent are delivered following the onset of spontaneous labor within 48 hours. In only 7 percent can delivery be delayed 48 hours or more after membrane rupture (“expectant management”). The time period from preterm ruptured membranes to delivery (latency) is inversely proportional to the gestational age when the membranes are ruptured. Thus, the earlier in gestation that PPROM occurs, the longer the latency interval until onset of labor.
DIAGNOSIS AND MANAGEMENT OF PRETERM RUPTURED MEMBRANES
1. In women with possible amnion rupture, one sterile speculum examination is performed to identify fluid coming from the cervix or pooled in the vagina. Demonstration of visible fluid is indicative of ruptured membranes and is usually accompanied by ultrasound examination to confirm oligohydramnios, to identify the presenting part, and to estimate gestational age. Nitrazine paper testing of vaginal pH has an appreciable false-positive rate associated with blood contamination, semen, or bacterial vaginosis. The microscopic inspection of cervicovaginal dried secretions for NaCl crystallization (ferning) also has an appreciable false-positive rate. Attempts are made to visualize the extent of cervical effacement and dilatation, but a digital examination is not performed.
2. If the gestational age is less than 34 weeks, but 24 weeks or more, and there are no other maternal or fetal indications for delivery, the woman is observed closely in the Labor and Delivery Unit. Continuous fetal heart rate monitoring is employed to look for evidence of cord compression, especially if labor supervenes.
3. If the fetal heart rate is reassuring, and if labor does not follow, the woman is transferred to the High Risk Antepartum Pregnancy Unit for close observation for signs of labor, chorioamnionitis, or fetal jeopardy.
4. If the gestational age is greater than 34 completed weeks and if labor has not begun following adequate evaluation, labor is induced with intravenous oxytocin unless contraindicated.
5. Betamethasone is given intramuscularly every 24 hours for 2 doses, for enhancement of fetal maturation. Dexamethasone may be used in lieu of betamethasone (see Chapter 35).
6. Ampicillin and gentamicin (clindamycin plus gentamicin in penicillin allergic women) are given intravenously for up to 48 hours to prolong the latency interval from membrane rupture to delivery. This therapy is not repeated later unless chorioamnionitis is diagnosed.
7. When labor is subsequently diagnosed, ampicillin, 2 g, is given intravenously every 6 hours prior to delivery for prevention of group B streptococcal infection in the neonate.
Management of Ruptured Membranes Before 24 Weeks
There are both maternal and infant risks to be considered when contemplating expectant management of ruptured membranes before 24 weeks. Maternal risks include the consequences of uterine infection and sepsis. Fetal risks include pulmonary hypoplasia and limb compression deformities, which have been associated with prolonged periods of oligohydramnios due to ruptured membranes.
Most obstetricians hospitalize women with pregnancies complicated by preterm ruptured membranes. Concerns about the costs of lengthy hospitalizations are usually moot because most women enter labor within a week or less of membrane rupture.
Assuming that no untoward perinatal outcome occurs due to an entangled or prolapsed cord or from placental abruption, the greatest concern with prolonged membrane rupture is the risk of maternal or fetal infection. If chorioamnionitis is diagnosed, prompt efforts to affect delivery, preferably vaginally, are initiated. Unfortunately, fever is the only reliable indicator for making this diagnosis; a temperature of 38°C (100.4°F) or higher accompanying ruptured membranes implies infection. Maternal leukocytosis by itself has been found to be unreliable.
For further reading in Williams Obstetrics, 23rd ed.,
see Chapter 36, “Preterm Birth.”