Role of prostaglandin-induced cervical changes in labor induction.

The role of the cervix in labor induction has been studied in a previous report. Cervical preparation by mechanical methods did not alter the course of induced labor. The same hypothesis is further elucidated in the present study using prostaglandin E2 vaginal suppositories for cervical preparation. Forty-seven pregnant women near term with Bishop scores of 4 or less were divided into three study groups: control subjects, oxytocin-treated patients, and prostaglandin group. A 12-hour preparation phase procedure was carried out to produce cervical and/or myometrial changes. All women had continuous measurement of uterine activity by an extraovular catheter. At the end of the preparation phase, the Bishop score was reevaluated, amniotomy carried out in all patients, and oxytocin infusion either started or continued. Although prostaglandin and oxytocin both significantly changed the cervix, oxytocin had the shortest induction-to-delivery interval, though the prostaglandin-treated group required lower concentrations of oxytocin. The authors conclude that with rigid control of Bishop score and timing of amniotomy and oxytocin infusion rates, prostaglandin-induced cervical changes alone did not uniquely benefit labor induction in the doses used, or within the time frame of the study.