The rising tide: Trends in induction of labor at term

The rate of induction of labor (IOL) has been increasing over the past 10years. Traditionally, IOL was utilized when it was deemed that the risk of continuing the pregnancy outweighed the benefit. This could be due to prolonged pregnancy past 41-42 weeks; gestation (post-dates), suspected maternal or fetal complications, or prolonged spontaneous rupture of membranes (PSROM) without spontaneous onset of labor. However, as more recent evidence has demonstrated reduced maternal and neonatal adverse events among patients undergoing elective IOL (eIOL) compared with expectantly managed patients, there has been a change in attitude towards eIOL in the normal-risk woman. The commentary regarding eIOL has been fraught with controversy. Despite concerns expressed by some healthcare providers, professional medical organizations have welcomed the concept of elective, risk-reducing induction as a reasonable option for patient choice.

Although it is acknowledged that IOL rates (as well as cesarean birth rates) are increasing, it is less obvious what are the causes of the rising IOL rates. Additionally, it is unclear to what degree various indications for IOL influence both the overall induction rate and the cesarean delivery (CD) rate. There is lack of clarity as to whether the higher-risk population undergoing medically indicated IOL (mIOL) contribute more to the increasing CD rates, as theorized or whether eIOL plays a significant role in these trends.

A retrospective observational cohort study evaluated the outcomes of patients who were delivered following IOL from 2018 to 2022 inclusive at the largest obstetric hospital in Ireland.

The primary objectives were:

1. To examine overall rates of IOL over a 5-year period.

2. To assess the trends in indications for IOL from 37 weeks' gestation over a 5-year period.

3. To assess the contribution of individual indications for IOL to the overall CD rate over each of the past 5 years.

A total of 36,938 women (16,155 nulliparous and 20,783 multiparous) were delivered during the 5-year study period, of whom 8072 nulliparous and 6343 multiparous women underwent IOL. There was a significant increase in rates of induction, increasing from 42% to 57% (P<0.001) in nulliparous women, and from 27% to 33% (P<0.001) in multiparous women. The highest contributions to the hospital CD rate were from those being induced for ‘fetal’ (5%), spontaneous rupture of membranes (‘SROM’) (4%), and ‘maternal’ (4%) reasons, with the lowest CD rates in the eIOL category (<1%) in both groups.

These data confirm a significant increase in rate of IOL over the 5-year period. The most common indications for IOL were fetal and maternal reasons. The incidence of medical comorbidity in pregnancy is climbing, resulting in a greater prevalence of high risk pregnancies. This, in turn, raises challenges in providing care to more complex patients. It is possible that the higher induction rate for fetal and maternal indications is a consequence of the higher risk patient.

This study offers insights into rising IOL rates by providing information on the likelihood of CD in groups with specific IOL indications. With these data, obstetricians have access to reliable information for shared decision-making with women and can offer appropriate counseling to those planning IOL about the risks of CD for the patient-specific indication. This study also shows that the CD rates and contribution to the overall CD rate were relatively stable throughout each of the past 5 years. Falling vaginal birth after cesarean section attempts and success rates is a noteworthy contributor to the overall increased CD rates.

Overall, in the era of shared decision-making and using data to empower women to make fully informed choices regarding their plan of care, this study provides group-specific information that can be used to optimally counsel women regarding the role of IOL in their obstetric care plan.

Source: NICHOLSON et al.; Int J Gynecol Obstet. 2024;00:1–8 DOI: 10.1002/ijgo.16054