Does induction of labor without a medical indication explain the overall increase in the induction rate: an observational study before and after the ARRIVE trial.

Abstract

Background: The rate of induction of labor increased particularly after the publication of ARRIVE trial conducted in low-risk primiparous patients without medical indication. However, this increase of induction rate does not seem to concern this population alone. Our aim was to understand how induction rate have evolved according to its indications and the impact on cesarean rate.

Methods: This was a retrospective observational study in a tertiary university maternity unit, including all women who gave birth between January 1st 2014 and December 31th 2021, at more than 24 weeks of gestation with a liveborn infant weighing ≥ 500 g (N = 9,523). We described the frequency of induction and caesarean section per year within the maternity unit. We differentiated two study periods: 2014-2017 and 2018-2021. We used the Grenoble classification to analyse the contribution of each of group to the overall induction rate and calculated the absolute and relative difference in induction rate for each group between the two periods. We analysed changes in the risk of caesarean section in each of the groups.

Results: The overall induction rate increased from 19.3 to 27.4% between 2014 and 2021 (p < 0.01). The cesarean section rate for women who underwent induction decreased significantly from 29.5% in 2014 to 25.2% in 2021 (p < 0.01). The induction rate moderately increased in the group corresponding to induction of labor "without medical indication" (relative difference of 14.9%; 95%CI [6.0;21.0]). The groups with the greatest increase in their induction rate between the two study periods were the breech group (relative difference of 66.7% 95%CI [49.0;83.0]) and the fetal pathology induction group (relative difference of 75.5% 95%CI [61.2;90.1]). The rate of cesarean among inducted women reduced significantly in the group of "multiple pregnancies" (aOR = 0.6; 95%CI [0.4;0.9]) and in the group of "maternal pathologies" (aOR = 0.8; 95%CI [0.6;0.9]). For the group 8 "induction without medical induction" the reduction was not significant (aOR = 0.8; 95%CI [0.8;1.2]).

Conclusion: From 2014 to 2021, we observed a marked increase in the induction rate in our maternity unit. This increase was not associated with a change of the cesarean rate. Induction of labor without medical indication represent only a small part of the induction rate.