Two more research studies have added to the concern that women who undergo induction of labour are more likely to end up with a caesarean section than if their labour began naturally. The first, an analysis of the outcomes of nearly 45,000 women who gave birth in Brisbane, showed that, in women who were 37 or more weeks pregnant, induction of labour was associated with a lower chance of having a spontaneous vaginal birth (Zhao et al 2017). Women undergoing induction were more likely to have an emergency caesarean section for fetal compromise, but the perinatal outcomes were broadly comparable betwen the groups (Zhao et al 2017). In other words, no benefit was gained by the women and babies who underwent induction of labour in this data set.
The second study looked at 2851 women having their first baby in Pennsylvania, USA. Women who underwent induction of labour were found to be about twice as likely to deliver by caesarean (35.9%) than women in spontaneous labor (18.9%). Much of this difference, the authors argued, can be explained by some of the factors associated with induction of labour: cervical dilatation <3 cm at hospital admission, fetal intolerance of labor, and dystocia. Only 6.2% of the ceasarean sections carried out on women who underwent induction of labour could be explained by factors associated with the reason given for induction of labour (Kjerulff et al 2017). In other words, it would appear that the vast majority of caesarean sections are a result of factors related to the induction process itself and not because of the condition of reason which led to induction being recommended. The authors conclude that, “increased risk of cesarean delivery after labor induction among nulliparous women is attributable mainly to lower cervical dilatation at hospital admission and higher rates of labor complications” (Kjerulff et al 2017).