Results of the RE-DINO multicenter randomized trial on the repeated use of vaginal dinoprostone (Propess®) for labor induction in patients at term.

Background: Labor is induced in over 25% of women in France. Prostaglandins, especially intravaginal dinoprostone (Propess®), are widely used to initiate cervical ripening. If labor does not start within 24 hours, there is uncertainty about whether to administer a second dinoprostone pessary or to use oxytocin to induce labor in order to achieve a vaginal delivery.

Objectives: Our principal objective was to determine whether placement of a second Propess®, followed by oxytocin (Syntocinon®) if necessary, in pregnant women for whom the first Propess® failed to induce cervical ripening increases the vaginal delivery rate compared to direct oxytocin injection. The vaginal delivery rate was therefore the primary outcome. The secondary outcomes were the cervical ripening failure rate and maternal and fetal morbidity and mortality.

Study design: RE-DINO is a prospective, open-label, multicenter, randomized superiority trial with two parallel arms running in 7 French hospitals. Patients at > 37 weeks of gestation who had unfavorable cervical conditions (Bishop score < 6) 24 hours after placement of the first Propess® (vaginal patch featuring progressive continuous diffusion of 10 mg dinoprostone), with fetuses in cephalic presentation, were included.

Results: 160 pregnant women were randomized, 80 patients in each group, from December 2016 through April 2022. Baseline characteristics such as age, BMI, maternal age at induction and Bishop score at induction were similar between both groups. Vaginal delivery occurred in 76.3% of cases in the 2^nd Propess^ࣨ group and 73.8% of cases in the Syntocinon® group (RR = 1.03 [0.86; 1.24], p=0.715). Although the cesarean section rate was similar in each group, there were significantly more cesarean sections for arrest of dilatation (52.6% vs 19%; p=0.0262) in the Propess® group and a larger, borderline-significant difference in patients having operative vaginal delivery (24.6% vs 11.9%; p=0.07) for abnormal fetal heart rate (80% vs 29%; p=0.05). There was significantly more failure of cervical ripening in the Propess^ࣨ group (57.1% vs 19%; RR=2.59 ; 95% CI [1.64; 4.11]; p < 0.0001) and the interval between study treatment and delivery was also significantly longer (28.1h vs 9,7h; p<0.0001). There was a higher incidence of post-partum hemorrhage in the Propess^ࣨ group, although this was not significant (11.3% vs 5% ; p=0,15), but also more newborns with acidosis (39.3% vs 27.9% ; p=0.18) or severe acidosis (8,6% vs 3.4% ; p=0.27), more meconium fluid (11.3% vs 6.3% ; p =0.26) and transferred to intensive care (5% vs 2.5% ; p=0.68).

Conclusion: Our data showed no superiority of a second dinoprostone pessary over oxytocin in patients not responding to initial prostaglandins E2 maturation for labor induction. Repeated use of Propess® is not useful for induction of labor.