By: 16 November 2017
Labour induction at 40 weeks associated with lower risk of perinatal mortality

Labour induction at 40 weeks in nulliparous women aged 35 and older is associated with reduced risk of in-hospital perinatal death, according to an analysis of English Hospital Episode Statistics published in PLOS Medicine.

The observational study, conducted by Hannah E. Knight of the London School of Hygiene & Tropical Medicine, and colleagues, provides further evidence that induction at or near the due date may be safer than expectant management in this group.

Guidelines recommend induction of labour between 41 and 42 weeks of gestation to prevent the risks associated with prolonged pregnancy. Women having their first baby at age 35 years or over are at increased risk of pregnancy complications, including perinatal death. To better understand the risks and benefits of elective induction in this group, Knight and colleagues analysed a national dataset of 77,327 such mothers giving birth between 2009 and 2014. They found that induction of labour at 40 weeks (compared with expectant management) was associated with a lower risk of in-hospital perinatal death (0.08 per cent versus 0.26 per cent; adjusted risk ratio [adjRR] 0.33; 95 per cent confidence interval [CI] 0.13-0.80, P = 0.015) and meconium aspiration syndrome (0.44 per cent versus 0.86 per cent; adjRR 0.52; 95 per cent CI 0.35-0.78, P = 0.002). Induction at 40 weeks was also associated with a slightly increased adjusted risk of instrumental vaginal delivery (adjRR 1.06; 95 per cent CI 1.01-1.11, P = 0.020) and emergency caesarean section (adjRR 1.05; 95 per cent CI 1.01-1.09, P = 0.019). The number needed to treat (NNT) analysis indicated that 562 (95 per cent CI 366-1,210) inductions of labour at 40 weeks would be required to prevent one perinatal death.

Unmeasured confounding may have influenced these results, and inductions and/or outcomes may have been under-recorded in the database. However, this association provides evidence that, as the authors state, “[b]ringing forward the routine offer of induction of labour from the current recommendation of 41-42 weeks to 40 weeks of gestation in this group of women may reduce overall rates of perinatal death.”

Source: PLOS.

Reference: Hannah E. Knight, David A. Cromwell, Ipek Gurol-Urganci, Katie Harron, Jan H. van der Meulen, Gordon C. S. Smith. Perinatal mortality associated with induction of labour versus expectant management in nulliparous women aged 35 years or over: An English national cohort studyPLOS Medicine, 2017; 14 (11): e1002425 DOI: 10.1371/journal.pmed.1002425