Comparison of Two Rhythm of Administration of Prostaglandin Gel for Induction of Labor

Approximatively 22% of pregnant women have an induction of labor in France (22.9% in our institution in 2019), mainly for prolonged pregnancy after 41 weeks gestational age or prolonged rupture of membranes. Patients whose cervix is considered unripe (Bishop score under 6) are generally proposed a cervical priming because induction of labor without prior priming entails a higher of cesarean delivery rate for failed induction. The devices used for cervical priming are pharmacological (mainly prostaglandin gel, pessaries or suppositories) or mechanical (Foley catheter, Cook balloons). Very few recommendations exist regarding the type of device, the rhythm and maximal number of repeat administrations and the interval between two administrations. Shortening interval between two administrations (in case of use of a device necessitating serial prescriptions) may shorten the time interval between beginning of priming and delivery. In our institution, a vaginal gel can be given three times before induction of labor with oxytocin and amniotomy, whatever Bishop score has been obtained after priming. These gels are given on a daily basis. This rhythm implies than for some women not responding to a first gel, priming can last up to three days, lengthening hospital stay and leading to maternal weariness. Maternal satisfaction during induction of labor is seldom analyzed. An intensification in gel administration implies a change in maternal management during the induction process, with shortened periods of rest between two gels and nearer periods of pain and discomfort, albeit on a theoretically shorter period. The way patients deal with this new rhythm compared to the classical in part of the evaluation in this study. All patients having a singleton pregnancy and an indication for term (≥ 37 weeks gestation age) induction with an unfavorable cervix and no contraindication to vaginal delivery will be eligible. Patients with fetuses in breech presentation, a scarred uterus, under 18 years, bearing a fetus with antenatally known malformation, not fluent in French or presenting an allergy to prostaglandins will be excluded. A written informed consent will be required before inclusion. The primary outcome will be the duration between first priming with prostaglandin gel and delivery. Secondary outcomes will be the satisfaction of patients with their induction process (measured through a survey answered during the in-hospital post-partum stay), the rate of cesarean section, the rate of hypertonia/hypercinesia during priming and induction requiring medical intervention, the length of active phase of labor (after 5 cm of dilation), the oxytocin doses used during delivery for induction or augmentation, initial neonatal (Apgar score, arterial cord pH and lactates, resuscitation maneuvers, transfer to intensive care unit) and maternal (post-partum hemorrhage, hyperthermia during labor, perineal laceration > 2nd degree and endometritis) morbidity and length of total hospital stay. The investigators calculated that a sample of 268 patients (134 in each group) will be necessary to detect a 30% reduction in duration between first priming and delivery in the experimental group (one gel every 12h) compared with the classical group. Mean time frame between first priming and delivery has been measured in our department in 2018 to 31.8 hours (standard deviation 27.6 hours).