The effects of labour induction at 39weeks in low-risk nulliparous women.

Abstract

Commentary on: Grobman WA, Rice MM, Reddy UM, et al. Labor Induction versus Expectant Management in Low-Risk Nulliparous Women. N Engl J Med 2018; 379(6):513-523. PMID 30089070. This trial attempts to address the practice of elective induction starting only at 41 weeks, a practice recommended by ACOG yet based on low-quality evidence 1. The authors randomised low-risk nulliparous women to either induction at 39 weeks, or expectant management with delivery prior to 42 weeks two days. A smaller trial based on the UK among women aged 35 years and older compared similar groups and found no significant effects on either the maternal or the infant outcomes for elective induction at 39 weeks 2. For this trial, a composite outcome of perinatal death and nine ‘serious neonatal complications’ was used for the primary outcome. A strength of this study was the prespecified definition of this composite outcome and the reporting of individual components. While the use of a composite outcome increases statistical power, it also limits interpretation because the included complications are not all of equal importance. There was a 20% relative reduction in this outcome in the early induction group (P = 0.049), with no difference between groups in the most serious outcome – perinatal death. The authors concluded that this P value did not reach statistical significance because they had a priori determined that only a P-value of less than 0.046 would indicate statistical significance due to a pre-planned interim analysis. The authors are to be commended for their intellectual honesty and rigor in interpreting their results. How should clinicians interpret these results and use them in practice? This trial was conducted in University and Community Hospitals, included all types of maternal providers, and did not stipulate a method for induction which all favours generalisability. However, 16 000 eligible women declined to participate, which could indicate sampling bias. Also, blinding or masking was not possible due to the nature of the intervention, which could have led to performance and ascertainment bias. With those caveats, the implications for practice are as follows: First, this trial provides reassurance that induction of labour at 39 weeks in a select population of low-risk nulliparous women is likely not harmful to women, and may be beneficial. Second, it provides reassurance that induction at 39 weeks in a select population of low-risk women is unlikely to cause neonatal harm (based on the upper limit of the confidence interval at 1) and may potentially be associated with up to a 36% decrease in adverse neonatal outcomes. Ultimately, providers must consider whether their patients fall within that select population. If these results are extrapolated to the estimated 1 282 544 low-risk, first-time deliveries in the US in 2016 3, the absolute risk reduction of 1.1% in the primary outcome, while appearing small, would translate into over 10 000 fewer women with perinatal complications annually. The 3.6% absolute risk reduction in Caesarean delivery would translate into 46 000 fewer Caesarean deliveries annually, and along with a reduction in the length of stay, may carry significant cost savings and a reduction in the pain and complications that ensue from such deliveries. https://ebneo.org/2019/01/labor-induction-at-39-weeks/ None. None.