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Premature rupture of membranes (PROM) is the single most common diagnosis associated with preterm delivery. Premature rupture of membranes is defined as rupture of bag of waters prior to the onset of labor. Preterm PROM is defined as rupture of membranes prior to term. Prolonged rupture of membranes consists of rupture of membranes for more than 24 hours. The latent period is the time interval from rupture of membranes to the onset of regular contractions.
Many cases of preterm PROM are caused by idiopathic weakening of the membranes, many of which are caused by subclinical infection. Other causes of PROM include hydramnios, incompetent cervix, abruptio placentae, and amniocentesis.
Maternal and Neonatal Complications. Labor usually follows shortly after the occurrence of PROM. 90% of term patients and 50% of preterm patients go into labor within 24 hours after rupture. Patients who do not go into labor immediately are at increasing risk of infection as the duration of rupture increases. Chorioamnionitis, endometritis, sepsis, and neonatal infections.
Perinatal risks with preterm PROM are primarily complications from immaturity, including respiratory distress syndrome, intraventricular hemorrhage, patent ductus arteriosus, and necrotizing enterocolitis. Premature gestational age is a more significant cause of neonatal morbidity than is the duration of membrane rupture.
Diagnosis is based on history, physical examination, and laboratory testing. The patient's history alone is correct in over 90% of patients. Urinary leakage or excess vaginal discharge are sometimes mistaken for PROM.
Sterile speculum exam is the first step in confirming the suspicion of PROM. Digital examination should be avoided.
The general appearance of the cervix is assessed visually, and prolapse of the umbilical cord or a fetal extremity should be excluded. Cultures for group B streptococcus, gonorrhea, and chlamydia are obtained. A pool of fluid in the posterior vaginal fornix supports the diagnosis of PROM. The presence of amniotic fluid is confirmed by nitrazine testing for an alkaline pH. Amniotic fluid causes nitrazine paper to turn dark blue because the pH is above 6.0-6.5. Nitrazine may be false-positive with contamination from blood, semen, or vaginitis.
If pooling and nitrazine are both non-confirmatory, a swab from the posterior fornix should be smeared on a slide, allowed to dry, and examined under a microscope for "ferning," indicating amniotic fluid. Ultrasound is useful to confirm the diagnosis, but oligohydramnios may be caused by other disorders besides PROM.
Assessment of PROM
The gestational age must be carefully assessed. Menstrual history, prenatal exams, and previous sonograms are reviewed. An ultrasound examination should be performed. The patient should be evaluated for the presence of chorioamnionitis (fever, leukocytosis, maternal and fetal tachycardia, uterine tenderness, foul-smelling vaginal discharge). Fever (temperature over 38°C) is indicative of chorioamnionitis. The patient should be evaluated for labor, and a sterile speculum examination should assess cervical change. The fetus should be evaluated with heart rate monitoring because PROM increases the risk of umbilical cord prolapse and fetal distress caused by oligohydramnios.
Treatment of Premature Rupture of Membranes
Term Patients
At 36 weeks and beyond, management of PROM consists of delivery. Patients in active labor should be allowed to progress.
Patients with chorioamnionitis, who are not in labor, should be immediately induced with oxytocin (Pitocin).
Patients who are not yet in active labor (in the absence of fetal distress, meconium, or clinical infection) may be discharged for 48 hours, and labor usually follows. If labor has not begun within a reasonable time, induction with oxytocin (Pitocin) is appropriate. Use of prostaglandin E2 is safe for cervical ripening.
Preterm Patients
Preterm patients with PROM prior to 36 weeks are managed expectantly. Delivery is delayed for the patients who are not in labor, not infected, and without evidence of fetal distress. Patients should be monitored for infection. Cultures for gonococci, Chlamydia, and group B streptococci are obtained. Symptoms, vital signs, uterine tenderness, odor of the lochia, and leukocyte counts are monitored. Suspected occult chorioamnionitis is diagnosed by amniocentesis for Gram stain and culture.