Role of the cervix in the induction of labor.

A study on induction of labor was carried out to test the hypothesis that changing the cervix will enhance the effectiveness of induction of labor. Fifty pregnant women near term with Bishop scores of 4 or less were divided into 5 study groups, in which a 12-hour preparation phase procedure was carried out to produce cervical or myometrial changes. All women had continuous measurement of uterine activity by an extraovular catheter. The patients were divided into 1) control subjects, and into groups treated with 2) laminaria, 3) Foley catheter, 4) amniotomy, and 5) oxytocin infusion. These preparation techniques were used for 12 hours, after which rupture of membranes was carried out in all cases. Although all procedures significantly changed the cervix, none but oxytocin affected the induction-to-delivery interval. The authors concluded that when a study design rigidly controls for cervical Bishop score, timing of rupture of membranes, and oxytocin infusion rates, the cervical preparation alone will not enhance inducibility.