Canadian Trial
Elective induction of labor now occurs in 21%–30% of all births, noted Dr. Marie-Danielle Dionne, a fetal-maternal medicine specialist at the University of Montreal. “An improved Bishop score before induction increases the rate of vaginal birth.”
She and her coinvestigators enrolled women with a normal singleton pregnancy at term who had intact membranes and an unfavorable cervix, with a Bishop score of 5 or less. Women were ineligible if they had prostaglandin hypersensitivity, previous uterine surgery, a noncephalic fetal presentation, or nonreassuring fetal cardiac monitoring.
The women were randomized in equal numbers to nonblinded treatment with a Foley catheter plus intravenous oxytocin infusion, a Foley catheter plus intravaginal misoprostol, or intravaginal misoprostol alone.
The trial was stopped early because of an elevated rate of cesarean deliveries in the first group, according to Dr. Dionne.
Intention-to-treat analyses were based on 92 women in the Foley plus oxytocin group, 85 women in the Foley plus misoprostol group, and 88 women in the misoprostol-only group.
On average, the women were 30 years old, and the median gestational age was 40.5 weeks. About three-fourths of the women were nulliparous. The mean Bishop score was 3. The leading indications for induction were a postdate pregnancy (54%) and diabetes (27%).
Trial results showed that the rate of delivery within 24 hours, the primary outcome, was highest in the Foley plus oxytocin group at 94%, Dr. Dionne reported. It was statistically similar in the Foley plus misoprostol group at 87%, but significantly lower in the misoprostol-only group at 74%.
However, the rate of cesarean delivery was 44% in the Foley plus oxytocin group. It was significantly lower in both the Foley plus misoprostol group at 24%, and in the misoprostol-only group at 28%.
The three groups did not differ with respect to rates of maternal complications (postpartum hemorrhage, hyperstimulation, receipt of antibiotics, and placental retention) and fetal and neonatal outcomes (Apgar scores, cord blood arterial pH, admission to the neonatal intensive care unit, meconium in amniotic fluid, receipt of antibiotics, and nonreassuring fetal monitoring).
“We can say that in our institutions, the use of a Foley catheter is associated with more deliveries within 24 hours,” said Dr. Dionne.
“This is mostly due to a smaller delay from induction to labor,” she said.
“Misoprostol use significantly reduced the rate of c-section, with or without a Foley catheter,” she further noted.
Dr. Dionne speculated that the higher rate of cesareans with the Foley catheter plus oxytocin, despite the more rapid delivery, was due to inadequate cervical ripening in the face of contractions. “There is a small change in the cervix and there are regular contractions, but it is probably not as physiological as with the misoprostol,” she said.
“So we have to decide which is best: more deliveries within 24 hours or more vaginal births,” Dr. Dionne concluded. “The answer is easy for me: We think more vaginal births is better.”