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Woman being induced

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.

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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; 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.

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; 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.

Induction of labour for improving birth outcomes for women at or beyond term

Published on 10 May 2018

Middleton, P.,Shepherd, E.,Crowther, C. A.

Cochrane Database Syst Rev Volume 5 , 2018

BACKGROUND: Beyond term, the risks of stillbirth or neonatal death increase. It is unclear whether a policy of labour induction can reduce these risks. This Cochrane review is an update of a review that was originally published in 2006 and subsequently updated in 2012 OBJECTIVES: To assess the effects of a policy of labour induction at or beyond term compared with a policy of awaiting spontaneous labour or until an indication for birth induction of labour is identified) on pregnancy outcomes for infant and mother. SEARCH METHODS: We searched Cochrane Pregnancy and Childbirth's Trials Register, ClinicalTrials.gov and the WHO International Clinical Trials Registry Platform (ICTRP) (9 October 2017), and reference lists of retrieved studies. SELECTION CRITERIA: Randomised controlled trials (RCTs) conducted in pregnant women at or beyond term, comparing a policy of labour induction with a policy of awaiting spontaneous onset of labour (expectant management). We also included trials published in abstract form only. Cluster-RCTs, quasi-RCTs and trials using a cross-over design are not eligible for inclusion in this review.We included pregnant women at or beyond term. Since a risk factor at this stage of pregnancy would normally require an intervention, only trials including women at low risk for complications were eligible. We accepted the trialists' definition of 'low risk'. The trials of induction of labour in women with prelabour rupture of membranes at or beyond term were not considered in this review but are considered in a separate Cochrane review. DATA COLLECTION AND ANALYSIS: Two reviewers independently assessed trials for inclusion, assessed risk of bias and extracted data. Data were checked for accuracy. We assessed the quality of evidence using the GRADE approach. MAIN RESULTS: In this updated review, we included 30 RCTs (reporting on 12,479 women). The trials took place in Norway, China, Thailand, the USA, Austria, Turkey, Canada, UK, India, Tunisia, Finland, Spain, Sweden and the Netherlands. They were generally at a moderate risk of bias.Compared with a policy of expectant management, a policy of labour induction was associated with fewer (all-cause) perinatal deaths (risk ratio (RR) 0.33, 95% confidence interval (CI) 0.14 to 0.78; 20 trials, 9960 infants; moderate-quality evidence). There were two perinatal deaths in the labour induction policy group compared with 16 perinatal deaths in the expectant management group. The number needed to treat to for an additional beneficial outcome (NNTB) with induction of labour in order to prevent one perinatal death was 426 (95% CI 338 to 1337). There were fewer stillbirths in the induction group (RR 0.33, 95% CI 0.11 to 0.96; 20 trials, 9960 infants; moderate-quality evidence); there was one stillbirth in the induction policy arm and 10 in the expectant management group.For women in the policy of induction arms of trials, there were fewer caesarean sections compared with expectant management (RR 0.92, 95% CI 0.85 to 0.99; 27 trials, 11,738 women; moderate-quality evidence); and a corresponding marginal increase in operative vaginal births with induction (RR 1.07, 95% CI 0.99 to 1.16; 18 trials, 9281 women; moderate-quality evidence). There was no evidence of a difference between groups for perineal trauma (RR 1.09, 95% CI 0.65 to 1.83; 4 trials; 3028 women; low-quality evidence), postpartum haemorrhage (RR 1.09 95% CI 0.92 to 1.30, 5 trials; 3315 women; low-quality evidence), or length of maternal hospital stay (average mean difference (MD) -0.34 days, 95% CI -1.00 to 0.33; 5 trials; 1146 women; Tau(2) = 0.49; I(2) 95%; very low-quality evidence).Rates of neonatal intensive care unit (NICU) admission were lower (RR 0.88, 95% CI 0.77 to 1.01; 13 trials, 8531 infants; moderate-quality evidence) and fewer babies had Apgar scores less than seven at five minutes in the induction groups compared with expectant management (RR 0.70, 95% CI 0.50 to 0.98; 16 trials, 9047 infants; moderate-quality evidence).There was no evidence of a difference for neonatal trauma (RR 1.18, 95% CI 0.68 to 2.05; 3 trials, 4255 infants; low-quality evidence), for induction compared with expectant management.Neonatal encephalopathy, neurodevelopment at childhood follow-up, breastfeeding at discharge and postnatal depression were not reported by any trials.In subgroup analyses, no clear differences between timing of induction (< 41 weeks versus >/= 41 weeks' gestation) or by state of cervix were seen for perinatal death, stillbirth, NICU admission, caesarean section, or perineal trauma. However, operative vaginal birth was more common in the inductions at < 41 weeks' gestation subgroup compared with inductions at later gestational ages. The majority of trials (about 75% of participants) adopted a policy of induction at >/= 41 weeks (> 287 days) gestation for the intervention arm. AUTHORS' CONCLUSIONS: A policy of labour induction at or beyond term compared with expectant management is associated with fewer perinatal deaths and fewer caesarean sections; but more operative vaginal births. NICU admissions were lower and fewer babies had low Apgar scores with induction. No important differences were seen for most of the other maternal and infant outcomes.Most of the important outcomes assessed using GRADE had a rating of moderate or low-quality evidence - with downgrading decisions generally due to study limitations such as lack of blinding (a condition inherent in comparisons between a policy of acting and of waiting), or imprecise effect estimates. One outcome (length of maternal stay) was downgraded further to very low-quality evidence due to inconsistency.Although the absolute risk of perinatal death is small, it may be helpful to offer women appropriate counselling to help choose between scheduled induction for a post-term pregnancy or monitoring without (or later) induction).The optimal timing of offering induction of labour to women at or beyond term warrants further investigation, as does further exploration of risk profiles of women and their values and preferences. Individual participant meta-analysis is likely to help elucidate the role of factors, such as parity, in influencing outcomes of induction compared with expectant management.

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