Study strengths and limitations
The IMPROVE trial had a triple-blinded study design with an intention-to-treat paradigm and good follow-up. There was also standardization of PGE1 administration criteria, which was consistent with the American College of Obstetricians and Gynecologists standards of care. Results were similar to those of prior studies regarding rates of tachysystole, urgent cesarean delivery, and vaginal delivery.
The study has good generalizability as it included both elective and medically indicated inductions; however, patients with ruptured membranes were excluded. Although there was no difference in the overall cesarean delivery rates, the study was underpowered to look at this outcome. The authors included a patient satisfaction survey, but this is hard to interpret since study participants all received tablets orally and vaginally. The study did not address efficacy of VM versus BM administration at different doses or time intervals.
WHAT THIS EVIDENCE MEANS FOR PRACTICE
Labor induction has doubled over the past 2 decades, with almost 25% of parturients currently undergoing induction in the United States.3 This number is likely to increase given recent data suggesting that routine induction at 39 weeks may significantly decrease cesarean delivery rates.4 It is critical, therefore, that we identify the optimal technique for cervical ripening, including the ideal dosing regimen and route of administration. Results of the IMPROVE trial suggest that vaginal administration of misoprostol (25 μg initial dose, 50 μg subsequent doses) may be superior to the buccal route, with more rapid vaginal delivery, more vaginal deliveries within 24 hours, and fewer urgent cesareans for nonreassuring fetal testing (although the overall cesarean delivery rate was not significantly different).
ERROL R. NORWITZ, MD, PHD, MBA; JULIE M. STONE, MD