Spontaneous premature rupture of membranes (PROM) occurs at term in approximately 10 percent of pregnancies. Induction of labor usually is indicated to prevent adverse maternal and neonatal outcomes. Management strategies for PROM at term include expectant management and active induction. Each strategy has risks and benefits. Various methods of labor induction are available, and oxytocin (Pitocin) is the pharmacologic agent most commonly used. Oral administration of mifepristone (Mifeprex) has been studied in other settings and has been shown to improve outcomes. However, it has not been studied in women with PROM at term. Wing and colleagues evaluated the use of oral mifepristone in women with PROM near term to determine whether it would hasten labor.

The trial compared the use of mifepristone with oxytocin in pregnant women who were at or beyond 36 weeks’ gestation and in whom PROM had occurred. Inclusion criteria for the study were singleton gestation, cephalic presentation, reactive fetal heart rate pattern, and the mother was 18 years or older. PROM was determined by gross pooling of amniotic fluid in the vaginal vault, positive nitrazine tests, and the presence of ferning on microscopy. Patients were randomized to receive 200 mg of oral mifepristone or intravenous oxytocin by standard protocol. The participants who received mifepristone were observed and switched to oxytocin if they failed to progress to the active phase of labor or when cervical ripening was adequate. The primary outcome of the study was duration from the start of treatment to delivery. Other outcomes assessed included route of delivery, need for oxytocin augmentation after mifepristone administration, and neonatal outcomes.

A total of 65 women were included in the study, of whom 33 were assigned to mifepristone. The average interval between the start of the induction to delivery was 1,194 minutes in the mifepristone-treated group versus 771 minutes for the group that received oxytocin. Significantly more women who were treated with oxytocin delivered vaginally within 24 hours compared with those treated with mifepristone (78.1 versus 51.5 percent, respectively). There was no difference in the number of vaginal deliveries between the groups. Significantly more fetal distress was noted in the mifepristone group than in the oxytocin group. In addition, a significant number of neonates in the mifepristone group were admitted to the neonatal intensive care unit compared with the oxytocin group.

The authors conclude that oral mifepristone administered 18 hours before oxytocin infusion did not improve labor stimulation in women who were near or at term with spontaneous PROM. They add that the use of mifepristone in this situation resulted in more adverse fetal outcomes compared with standard oxytocin infusion.