The rising tide: Trends in induction of labor at term
The rate of induction of labor (IOL) has been increasing
over the past 10 years. 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
