Weight gain regardless of pre-pregnancy BMI and influence of fetal gender in response to labor induction in postdate pregnancy

Objective: To evaluate whether maternal weight and body mass index (BMI) and their increase throughout pregnancy are associated with the response to labor induction in postdate pregnancies. Methods: A total of 376 nulliparous women carrying singleton postdate pregnancies with unfavorable cervix were enrolled. We considered as primary outcome vaginal delivery within 24h after induction, and outcomes were divided into responders (n=258) and non-responders (n=107) to the induction of labor to perform the statistical analyses. Results: In the total population of study, women who successfully delivered within 24h differed significantly from the remaining patients in terms of maternal weight gain (p=0.009) and BMI increase (p=0.02) during pregnancy. In addition, males were significantly more (p=0.005) than females among newborns of women not responding to induction of labor. In the multivariate analysis, maternal weight gain and fetal sex significantly influenced the induction response. The occurrence of a failed induction of labor was more likely in patients presenting a greater maternal weight gain (cut-off 12kg) and male fetus. Conclusion: Weight gain over 12kg regardless of pre-pregnancy weight and male fetal gender are two novel potential risk factors for the prediction of failure to induction of labor in postdate pregnancy