The rate of induction of labor during pregnancy has continued to increase in the United States over the past few years. Preinduction cervical ripening has been shown in some studies to improve the success rate of labor induction. Various pharmacologic and mechanical methods are available for cervical ripening. The pharmacologic methods, which include dinoprostone and misoprostol preparations, are the most commonly used methods. The early mechanical ripening method used a natural material placed in the endocervical canal that absorbed water, expanded, and dilated the cervix. Inserting a Foley catheter in the endocervical canal and inflating the bulb is a newer, mechanical method that appears to offer significant advantages over the pharmacologic preparations. However, concerns about cervical trauma caused by the Foley catheter method have been raised. Sciscione and associates assessed the rate of preterm birth in subsequent pregnancies in women who received preinduction cervical ripening with a mechanical method or a pharmacologic method.
The study was a retrospective review of an obstetric database from July 1998 to July 2001. Charts were included for review if the patient had induced labor with preinduction cervical ripening, a singleton pregnancy, one preinduction method, no history of cervical incompetence, and a subsequent pregnancy. The patients were divided into two groups for analysis based on whether they received cervical ripening by Foley catheter or by a prostaglandin preparation. Patients were excluded if they received more than one of the cervical ripening methods.
Patients who used the Foley catheter method had a 16F Foley catheter inserted intracervically; the balloon was filled with 30 mL of sterile water. Traction was placed on the catheter, and the induction was started after the extrusion of the Foley. The prostaglandins were used following standard protocols. The primary outcome measure was preterm delivery (i.e., earlier than 35 weeks’ gestation). Other outcome measures included subsequent premature labor that required tocolysis, gestational age at delivery, need for inductions of labor, spontaneous labor, and spontaneous abortion.
A total of 126 women were included in the analysis. There were no significant demographic differences between the Foley catheter group and the prostaglandin ripening group. There also were no differences between the groups in subsequent deliveries with regard to maternal age, gravidity, parity, spontaneous or induced abortions, cone or loop electrosurgical excision procedures, history of cervical manipulation, need for induction, mode of delivery, episiotomy, gestational age at delivery, Apgar scores, labor duration, use of oxytocin, or birth weight. There were no significant differences between the groups in preterm birth at 37, 35, or 32 weeks’ gestation.
The authors conclude that the use of a Foley catheter for preinduction cervical ripening does not appear to increase the risk for preterm birth in subsequent pregnancies. They add that this method of cervical ripening appears to be effective and safe compared with the prostaglandin methods.