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NIHR Signal Inducing labour at or after 41 weeks reduces risks to infants

Published on 11 September 2018

doi: 10.3310/signal-000641

Inducing labour after the due date slightly lowers the risk of stillbirth or infant death soon after birth compared with watchful waiting. But the overall risk is very low. Induced deliveries may reduce admissions to the neonatal intensive care unit.

Pregnant women having induced labour are less likely to have a caesarean section than those who wait for labour to begin naturally. They may have a slightly higher chance of needing an assisted vaginal birth (for example, using forceps or vacuum extraction).

Many pregnancies continue for longer than the average 40 weeks. Because of the risks to infants, women are often offered the option of induced labour at between 41 and 42 weeks. However, induction also carries risks to mother and baby, which must be weighed against potential benefits.

The findings from a large review of 30 trials are in line with NICE guidance and may help women to make informed choices about whether or when to induce labour.

  •   Fertility and childbirth, Midwifery
Inducing labour at or after 41 weeks reduces risks to infants

Why was this study needed?

Pregnancies are considered to have reached term at 37 weeks, with most women going into labour by 41 weeks. Previous research has indicated a slightly increased risk of stillbirth and neonatal death for pregnancies that extend beyond 42 weeks. For this reason, women are offered to be induced between 41 and 42 weeks.

Approximately 1 in 5 labours in the UK is induced, accounting for around 122,000 births each year. Induction is usually done by inserting a prostaglandin (hormonal) tablet or gel into the vagina which softens the cervix. Induced labour may be more painful compared with spontaneous birth. Thus the decision on whether or not to be induced can be difficult.

This updated Cochrane review incorporates eight additional trials to see if labour induction at, or beyond term, reduces the risks for women with uncomplicated single pregnancies.

What did this study do?

This systematic review of 30 randomised controlled trials compared a policy of labour induction with one of expectant management for 12,479 pregnant women at or beyond term. The women were at low risk of complications.

The trials took place in high and middle-income countries with four from the UK. In 75% of the trials, induction occurred in the intervention group when pregnancies reached 41 weeks or beyond. Most trials offered induction to the expectant management group one week later.

Overall, the trials were at moderate risk of bias. However, 19 of them were conducted from 1969 to 2000, so it is likely that outcomes for both mother and baby would have improved since then.

What did it find?

  • Labour induction was associated with fewer all-cause infant deaths at or around the time of birth (1 per 1,000) compared with expectant management (3 per 1,000). There were two deaths in the induction of labour group including one stillbirth, and 16 in the expectant management group, including 10 stillbirths (risk ratio [RR] 0.33, 95% confidence interval [CI] 0.14 to 0.78; 20 trials, 9,960 infants). 
  • Rates of admission to the neonatal intensive care unit were similar at 7.5% for infants who were induced compared with 8.5% for expectant management (RR 0.88, 95% CI 0.77 to 1.01; 13 trials, 8,531 infants).
  • Slightly fewer babies in the induction group had Apgar scores of below seven at birth, which is an indication of poor health: 1.2% compared with 1.7% for expectant management (RR 0.70, 95% CI 0.50 to 0.98; 16 trials, 9,047 infants).
  • Induction resulted in fewer caesarean sections, 980/6,004 (16.3%) compared with 1,056/5,734 (18.4%) who had expectant management (RR 0.92, 95% CI 0.85 to 0.99; 27 trials, 11,738 women). Vaginal births involving forceps or vacuum extraction were similar at 20.6% of those induced compared with 19.3% for expectant management (RR 1.07, 95% CI 0.99 to 1.16; 18 trials, 9,281 women).
  • There was no clear difference in perineal trauma, bleeding after birth, or in the length of hospital stay between the two groups, although the quality of the evidence for these measures was low or very low.

Outcomes following induction of labour vs expectant management from 41 weeks of pregnancy

What does current guidance say on this issue?

The 2008 NICE guideline on inducing labour (updated in 2013) recommends that women with uncomplicated pregnancies should usually be offered labour induction between 41 and 42 weeks to avoid the risks of prolonged pregnancy. The exact timing should take woman's preferences and local circumstances into account. Women who choose expectant management should be offered increased monitoring from 42 weeks to ensure the baby’s safety.

WHO guidelines from 2011 also recommend induction of labour for women who are known to have reached 41 weeks of gestation.

What are the implications?

The evidence from this review supports and strengthens NICE and WHO guidelines on induction of labour.

The risk of infant death at or around the time of birth remains small, regardless of whether labour is induced or not. However, that risk is slightly lower for induction compared with expectant management.

There is a reduced risk of caesarean section and possibly an increased risk of operative vaginal birth if labour is induced, compared with expectant management.

This is likely to be the best available evidence, but we still do not know the best timing for induction. Women should be offered the option of labour induction at 41 to 42 weeks, together with information about these risks. 

Citation and Funding

Middleton P, Shepherd E, Crowther CA. Induction of labour for improving birth outcomes for women at or beyond term. Cochrane Database Syst Rev. 2018;(5):CD004945.

This project was funded by a National Institute for Health Research Systematic Reviews Programme Grant (project number 13/89/05) and other sources, including National Health and Medical Research Council, Australia.

Bibliography

NHS website. Inducing labour. London: Department of Health and Social Care; last reviewed 2017.

NICE. Inducing labour. CG70. London: National Institute for Health and Care Excellence; 2008.

NICE. Induction of labour. Evidence Update 44. London: National Institute for Health and Care Excellence; 2013.

WHO. WHO recommendations for induction of labour. Geneva: World Health Organization; 2011.

Expert commentary

Risks of post-term pregnancy include increased labour interventions and poorer infant outcomes. To reduce risk, induction may be recommended although optimal timing is debated. The intervention itself is not without risk.

This updated review of 30 trials with over 12,000 low-risk women compared outcomes of induction at or beyond term with spontaneous labour. Induction was associated with better infant outcomes and fewer caesarean births, with a small non-statistically significant increase in operative vaginal births. Findings should offer women and clinicians further reassurance about post-term induction. Nevertheless, care should be individualised to support women’s choices, including when induction is declined.  With increasing numbers of induced labours, we need to know more about women’s preferences and impacts on maternity services.

Debra Bick, Professor of Midwifery and Maternal Health/Editor in Chief ‘Midwifery’ journal, King’s College London