Outpatient use of prostaglandin gel for ripening of the cervix and induction of labor

Journal of Family Practice, June, 1990 by Mindy A. Smith, Lynn Swan, Barbara S. Caruthers, Caryl Heaton

Outpatient Use of Prostaglandin Gel for Ripening of the Cervix and Induction of Labor

The onset of labor, defined as uterine contractions that bring about progressive cervical dilation and effacement with descent of the presenting part, [1] is a complex process involving altered hormonal levels and interaction between both oxytocin and prostaglandins. [2-6] Before the onset of labor, the cervix undergoes a gradual process of ripening, involving a rearrangement of rigid collagen fibers into a more flexible configuration. [7] Hormonal factors, in association with increasing prostaglandin concentration, appear to play an important role. Bishop's description of pelvic scoring [8] and a more recent report by Lange et al [9] of the value of prelabor cervical condition in predicting the inducibility of labor led to the use of various methods for cervical ripening. [10-13] Of these methods the most physiologic and successful were those using prostaglandins. [7]

While the use of oxytocin as a uterine stimulant gained widespread acceptance in the early 1960s, it was not until 15 to 20 years later that prostaglandin use before induction as a cervical ripening agent underwent investigation in randomized placebo-controlled trials. [14-20] In addition to demonstrating successful cervical ripening, these studies reported a 30% to 60% rate of labor onset after either intracervical or intravaginal prostaglandin [E.sub.2] ([PGE.sub.2]) gel placement with few adverse effects. Several additional studies investigated dosing intervals of every 6 hours to every 12 hours but found no advantage to sequential gel application. [19] [21-23]

While these studies demonstrate the effectiveness of prostaglandin gel in preinduction ripening, the dosage, frequency, and method of gel application remain controversial. A recent placebo-controlled trial of outpatient cervical ripening with intravaginal [PGE.sub.2] gel in prolonged pregnancies demonstrated the safety and efficacy of a single gel application in both ripening and induction of labor, with 25% of 55 women in the gel group admitted in labor within 8 hours after gel placement. [24]

The purpose of the present study is to report the experience in a family practice outpatient center with the use of intravaginal [PGE.sub.2] gel for cervical ripening among patients with a medical or obstetric indication for induction. In compiling these data, specific attention was directed toward the indications for use of [PGE.sub.2] gel, the efficacy of cervical ripening or induction of labor through the use of single or repetitive [PGE.sub.2] gel placements, the subsequent need for oxytocin induction or augmentation of labor, and the safety of the protocol presented for the administration of the [PGE.sub.2] gel in the outpatient setting.

METHODS

Forty-five patients received [PGE.sub.2] gel for outpatient cervical ripening between July 1, 1987, and October 30, 1988, in the family practice center of the University of Michigan Department of Family Practice. The practice is located in a community of 3850 people, with an additional 14,000 people living in the surrounding townships. The community is part of a standard metropolitan statistical area within Washtenaw County and is therefore considered urban. The population is 98% white and the median household income is $22,499. Patients are seen by family practice faculty and residents for prenatal care, and their deliveries are attended by these physicians at the University of Michigan Hospital in Ann Arbor, Michigan. The decision to use [PGE.sub.2] gel was made on a case-by-case basis by the family practice resident or faculty physician with consultation with either the attending family physician or a university obstetric consultant.

The [PGE.sub.2] gel was prepared by grinding a whole 20-mg suppository (Prostin, Upjohn Company, Kalamazoo, Mich) and mixing it with 100 mL of sodium carboxymethylcellulose 2% gel. Samples of prostaglandin (2 mg) were drawn up into 5-mL plastic syringes and kept frozen. The gel was thawed at room temperature just before use.

The protocol for all [PGE.sub.2] gel insertions was as follows: (1) Before gel insertion, all patients underwent a nonstress test, which was considered reactive if two fetal accelerations (15-beat acceleration for 15 seconds or at least 10% of baseline) were seen associated with fetal movement within 10 minutes. (2) After a reactive nonstress test, the cervix was examined and a Bishop scored assigned. A 16-gauge angiocatheter tube was then connected to a gel-filled syringe, and the thawed gel was placed into the posterior vaginal fornix. (3) Patients were continuously monitored for an additional 30 minutes with an external fetal heart rate monitor and a uterine tocodynamometer. (4) Patients were instructed to call or return if contractions occurred as often as 5 minutes apart. An assessment of cervical change was performed on the return visit, as arranged by the physician, or at admission to the hospital in labor.