A double-blind randomized trial of two dose regimens of misoprostol for cervical ripening and labor induction

The objective of this study was to compare the efficacy and safety of two dosing regimens of misoprostol for cervical ripening and labor induction.

Patients who fulfilled the study criteria were randomized to received misoprostol 25 microg or 50 microg intravaginally every 3 h for a total of eight doses for cervical ripening or until labor was established. Endpoints for successful cervical ripening was achievement of Bishop score of nine or greater, and for labor induction reaching the active phase of labor in the first 24 h. The rates of success, duration of first and second stages of labor, type of delivery, significant side effects, and neonatal outcome were measured and compared between the two study groups. Two hundred and fifty-one patients were randomized in two groups--126 received 50 microg and 125 received 25 microg misoprostol. Demographics of the two study groups were similar.

Patients in the 50 microg group had a shorter first stage (848 min vs. 1,122 min, P < 0.007), shorter induction-to-vaginal delivery interval (933 min vs. 1,194 min, P < 0.013), decreased incidence of oxytocin augmentation (53.9% vs. 68%, P < 0.015), and decreased total units of oxytocin (2,763 mU vs. 5,236 mU, P < 0.023), but there was a higher hyperstimulation rate (19% vs. 7.2%, P < 0.005).

Successful induction rate, delivery types, and fetal outcome were similar in both groups. Although the rate of vaginal delivery and neonatal outcome were similar in both groups, the 50 microg regimen had shorter first and second stages of labor, and a higher hyperstimulation rate that was easily manageable, allowing for flexibility in using the higher dose in low-risk pregnancies.