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Evid Based Med 18:117-118 doi:10.1136/ebmed-2012-100862
  • Aetiology
  • Cohort study

Elective induction of labour is associated with decreased perinatal mortality and lower odds of caesarean section at 40 and 41 weeks

  1. Aaron B Caughey
  1. Department of Obstetrics and Gynecology, Oregon Health & Science University, Portland, Oregon, USA
  1. Correspondence to : Dr Aaron B Caughey
    OHSU, OB Gyn, 3181 SW Sam Jackson Park Road, Portland, OR 97239, USA; caughey{at}ohsu.edu

Commentary on: [Abstract/FREE Full text]

Context

Induction of labour can be utilised to intervene in a pregnancy when the risks of ongoing pregnancy outweigh that of intervention. Elective induction of labour is labour induction without a clear medical or obstetric indication. It is widely believed to increase caesarean delivery, posing unnecessary risks to mother and fetus.1 ,2 However, little objective information supports this conclusion, and a meta-analysis of randomised trials3 found that elective induction decreased caesarean delivery compared to expectant management (ie, allowing the pregnancy to progress, leading to delivery at a later gestational age).

While many past observational studies1 ,2 have found higher risk of adverse outcomes with elective induction, these studies have all had a major shortcoming. Such studies have been designed to compare induction of labour to spontaneous labour at the same gestational age—a comparison that is not clinically relevant and potentially misleading. The true clinical alternative to induction of labour is not immediate spontaneous labour, but rather allowing the pregnancy to progress with expectant management, which would lead to a gestational age at delivery beyond that of the induction of labour.

Methods

In the paper by Stock and colleagues the authors compared pregnancy outcomes between women who underwent an induction of labour without clear indication to expectant management as has been described previously.4 Thus, women with elective induction of labour at 37 weeks’ gestation were compared to those who progressed to 38 weeks and beyond. Unfortunately, the data utilised did not specifically contain indications for induction of labour, so the authors used documented conditions that can be used as indications for induction, such as hypertensive disorders, fetal abnormalities or diabetes.

Findings

Elective induction of labour was associated with a reduction in the primary outcome of perinatal mortality consistently at all gestational ages with adjusted ORs that ranged from 0.29 to 0.46, all statistically significant. It also led to a reduction in maternal morbidity at each week of gestation. Interestingly, with respect to caesarean delivery, elective induction of labour conferred a slight increase at 37, 38 and 39 weeks (adjusted ORs 1.02, 1.03 and 1.08, respectively, and only the latter statistically significant), but was associated with a reduction in caesarean delivery at 40 and 41 weeks’ gestation (adjusted ORs 0.85 and 0.78, respectively).

Commentary

While there are concerns about increasing intervention in obstetric populations, it is unclear what the true causal relationship is between elective induction of labour and a range of perinatal outcomes including caesarean delivery. The current paper goes beyond mode of delivery and demonstrates that the risk of perinatal mortality appears to be decreased in pregnancies undergoing elective induction of labour. This finding is not overly surprising, as the ongoing risk of stillbirth only continues throughout gestation. Similarly, a recent paper compared the risk of perinatal mortality between delivery and 1 week of expectant management and found it to be increased by expectant management at 39 weeks and beyond.5

The findings of a non-significant increase in the risk of caesarean delivery at 37 and 38 weeks, a small but statistically significant increase at 39 weeks, and a decrease in the risk of caesarean delivery at 40 and 41 weeks from elective induction of labour are confusing. Delivery at 37–39 weeks’ on a routine basis is much less common, so it may be the case that many of these deliveries actually had an indication that was not captured in their administrative data. For example, it does not appear that the authors utilised fetal growth restriction as an exclusion indication, and its inclusion in the induction group would increase the rate of caesarean delivery.

This study brings attention to an important issue that affects many millions of women worldwide annually. While the findings of the paper are intriguing, these data should be considered exploratory due to possible biases in this observational study. It should not be used to guide clinical practice with respect to improving perinatal mortality. However, with respect to risk of caesarean section associated with induction, the findings here may be confusing but meta-analyses of prospective, randomised trials have already shown a decrease in the risk of caesarean from induction. Thus, this information can be used to reassure women when counselling them about induction of labour.

Footnotes

  • Competing interests None.

References

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