Methods of induction of labor and women’s experience: a population-based cohort study with mediation analyses

Experience of induction of labor (IoL) is rarely assessed according to the method and results found in RCT are not extrapolable in current practice.

Negative experience of IoL can have short- and long-term effects on mother well-being and health and may be explained both by the methods and the outcomes of IoL.

Using population-based data, experience of Iol was less positive with cervical ripening. Experience of IoL was not different according to the ripening method and was only partly explained by the interventions and complications.

Multivariable Poisson regression models were performed to obtain risk ratios. A robust variance was used to take the cluster effect into account. For the mediation analysis, we used the inverse odds weighting (IOW) method described by Nguyen et al. [32, 33] IOW is a weight-based approach that condenses the association between the exposure and the mediator into a weight. It is a stepwise process. First, we estimated for each woman the predictive odds of ‘undergoing cervical ripening’ due to a ‘delivery with intervention or complications’. The inverse of this predicted odds gives a weight. Secondarily, the direct effect of cervical ripening on maternal experience was estimated by using weighted Poisson regression. Then, the indirect effect was calculated by subtracting the direct from the total effect coefficients. The proportion mediated (PM) was calculated as the ratio of the total effect to the indirect effect [34]. Confidence intervals for indirect effect and PMs were obtained by bootstrapping. Complete case analyses were performed because outcome data were missing for fewer than 2% of the women who responded to the questionnaire. The statistical analyses were performed with Stata/SE software, version 15.0.

Experience of induction of labor was less positive for women requiring cervical ripening. Women deplored a greater gap between what was expected and what was experienced, more unacceptable duration of labor, vaginal discomfort, intense pain, and insatisfaction with induction. Most of the experience was explained by the method and not by the interventions or complications of delivery. The women’s experience did not seem different between the prostaglandins but ripening with the balloon catheter seemed associated with less intense pain.

This is to our knowledge the first study to examine specifically multiple domains of the experience of IoL associated with cervical ripening with population-based data while taking into account the mediating role of interventions and complications. The MEDIP study was specifically designed to study perinatal outcomes associated with the different methods of induction of labor in France [19, 26]. The prospective data collection about the course of induction ensured the quality of the information reported.

Our study had some limits. A non-validated questionnaire was used, because the existing scales did not appear appropriate for a specific evaluation of the experience of IoL. Since the MEDIP study was performed, the EXIT scale (Experience of induction tool) has been developed in Australia for this purpose, but it has never been validated in another population [35]. External validity is also questionable because the women included came from perinatal networks not randomly selected, although characteristics of maternity units participating in this large sample were comparable to those of all French maternity units [26]. There was also a selection bias of respondent women who were most frequently European and employed. This questionnaire was sent at 2 months because memories of facts immediately after delivery may be modified, due to tiredness or lack of time to integrate the course of events. Moreover, interviewing women during their stay in the maternity unit may have led the woman interviewed to provide information that she felt comfortable with the care providers. We cannot know whether the responses were biased toward women with less or worse positive experience or not. Nonetheless, we showed that the response was not associated with interventions or complications. Finally, a strong proportion of the experience was probably affected by the environment of birth, the specific organization of a maternity ward or the individual relation created between the woman and the provider supporting and caring for her [36, 37]. Such information might have been particularly relevant for comparison of different cervical ripening methods, for which the usage are heterogeneous and depend on maternity unit’s preferences [26].

These data about how women experience IoL according to the method used might be relevant for guiding the management of care. Qualitative studies have already shown that a negative experience of induction was associated with a lack of preparation and information about the benefits and risks of induction and its course, to the intensity of pain, the duration of the induction and to a poorer medical outcome, in particular, emergency cesarean delivery [36, 37]. These studies didn’t distinguished specifically women with cervical ripening. When comparing woman satisfaction between oxytocin alone and vaginal prostaglandins E2, a meta-analysis of Alfirevic et al. [16] previously found no difference. However, the three trials included had a different way of measuring maternal satisfaction and the studies were probably not representative of actual obstetric practice.

The less positive experience of childbirth with cervical ripening does not imply that oxytocin should be proposed whatever the degree of cervix immaturity. Indeed, cervical ripening is recommended in case of unfavourable cervix [38, 39]. However, it calls for stronger support and counselling. In France, most pregnant women attend antenatal birth classes, especially the nulliparous women, but the content of these classes are probably very heterogeneous. Antenatal education on what to expect after induction on labor according to the method should probably be enhanced [13]. Moreover, one-to-one support for management of pain, which is not usual in French practices would certainly be good for improving maternal experience [37].

Our results also raise questions, as the number of elective IoL might be increased in the coming years. Indeed, recent data have demonstrated better perinatal outcomes with elective induction of labor at term, regardless of cervical status [40‐42]. In the ARRIVE trial comparing induction of labor with expectant management among 6000 low-risk nulliparous women at 39 weeks of gestation, induction of labor resulted in a better global experience and less pain [43]. Results were not stratified according to the method of induction. One limitation is that the experience of women who agreed to participate to such trial may not be representative of that of women in general population. They volunteered to participate and may have been more inclined to experience their induction positively whatever the method used. In the review of observational study comparing induction of labor with expectant management, women’s experience was not evaluated [42]. Our results can not imply that women who had unfavourable cervix expectantly managed instead of being induced would have had a better experience. However, in the absence of a medical indication, waiting for the cervix to be more favourable may be an alternative to improve maternal experience.

The few studies comparing the experience of different methods of cervical ripening also found greater discomfort and stronger pain during induction by prostaglandins compared with the balloon, but overall global satisfaction did not differ [44, 45]. This may be explained by the fact that the balloon appears to have a mechanical ripening action but not contraction-inducing effect that may be less painful. These results merit further exploration in view of the small number of women induced with the balloon included in these studies as in our study.