Retrospective evaluation of labor induction with scar uterus at the university hospital of Rennes

Objective: The aim of the study was a retrospective evaluation of labor induction in women with one previous cesarean section. The primary outcome was the mode of delivery. We also studied the severe maternal and neonatal morbidity and identify some prediction factors of vaginal delivery after labor induction after one previous cesarean section.Study design: This was a retrospective observational monocentric study performed over the period from January 1st, 2016 to April 30th, 2020 at the university hospital of Rennes. Were included women with scar uterus because of one previous cesarean section with a viable singleton fetus in cephalic presentation and an induction of labor for medical reason, at term. Multivariate logistic regression analysis was used to analyze prediction of vaginal delivery after labor induction after one previous cesarean section. We also studied maternal (included uterine rupture, loss of blood, obstetrical injury of anus sphincter) and neonatal (APGAR score, arterial umbilical pH after 1 minute of life and eventual admission to neonatal unit) morbidity. We used a stepwise multivariate logistic regression model to select variables for multivariate analysis. The model with the lowest Akaike Index Criteria was chosen.Results: The study enrolled 353 women with scar uterus: 121 women were induced by balloon catheter, 57 by osmotic cervical dilatators, 91 by oxytocin alone, 84 by amniotomy. Vaginal delivery rate was 47,9%. There was 45% of vaginal delivery in the group with Bishop < 6 before induction of labor versus 62% in the group with Bishop >= 6. There was no statistically significative difference in neonatal and maternal severe morbidities between vaginal delivery and cesarean section: 4,5% of severe maternal morbidities (n = 16). Among their, we highlighted 7 uterine ruptures (3,8%). We observed also 3% of postpartum severe hemorrhage in vaginal delivery group (n = 5) against 1,6% in cesarian section group (n = 3) with no statistical significant difference (p = 0,632). Regarding to the obstetric perineal tears and lacerations we noticed 1,2% of OASIS 3 (n = 2) and 0,6% of OASIS 4 (n = 1). Severe neonatal morbidities were comparable by mode of delivery without significant difference: APGAR score at 5 min was similar (p = 1), as well as arterial umbilical pH after 1 min. (p = 0.719) and admissions to a neonatal unit (p = 1). Two variables were statistically associated with vaginal delivery after labor induction in women with scar uterus: Bishop score >= 6 (OR = 0,44; 95%CI: 0,25-0,81) and/or previous vaginal delivery after cesarean section (OR = 0,17; 95%CI: 0,08-0,35).Conclusion: With 47,9% of vaginal delivery after labor induction in women with scar uterus, only 3.8% (n = 7/ 353) of uterine ruptures, less than 1% APGAR < 7 at 5 min (n = 3/353), induction on scar uterus should be consider in obstetrical practice. Bishop score >= 6 and/or previous vaginal delivery after cesarean section are associated to vaginal delivery after labor induction.