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This is a plain English summary of an original research article. The views expressed are those of the author(s) and reviewer(s) at the time of publication.
Planning to artificially start labour for older women, pregnant with their first child, in the 39th week of pregnancy does not affect the chance of having a caesarean delivery, according to a new trial funded by NIHR.
Older women having a first baby have a higher risk of stillbirth and other complications than younger mothers and inducing labour at or before the due date is thought to reduce this risk. However, there have been fears that inducing labour may raise the risk of a caesarean delivery.
This study found that women aged 35 or over having their first child and who were induced at 39 weeks had no higher risk of a caesarean (32%) than women who had standard wait-and-see care (33%) with intervention if necessary.
It’s important to note that this study did not investigate whether women whose labour was induced had a lower risk of stillbirth. A large trial is in progress to investigate this issue. In the meantime, the findings may reassure some women aged over 35 that labour induction may carry no more risk of having a caesarean than spontaneous labour.
Why was this study needed?
In industrialised countries, the average age of women at childbirth has been increasing since 1975, reaching 30.2 years in the UK by 2014. Since 1984, the birth rate for women aged over 35 has more than doubled.
The risks of unexplained stillbirths are higher for those aged over 35. This amounts to one stillbirth in every 735 births in the 39th or 40th week compared to one in 1020 for younger women. For this age group, the rate also increases with the length of pregnancy. The risk is one in 1220 in the 37th or 38th week of pregnancy rising to one in 735 in the 39th or 40th week of pregnancy.
Induction of labour at term (that is, when the baby is due) in older mothers is thought to reduce the stillbirth risk but there are worries that it may also increase the risk of an emergency caesarean.
This trial aimed to find out if induction of labour at 39 weeks of pregnancy in older women having their first baby had any effect on caesarean rates.
What did this study do?
This was a randomised controlled trial involving 619 women aged 35 or older who were having their first child. About half the women were assigned to having their labour induced between 39 weeks and 39 weeks six days of pregnancy and the other half assigned to standard care: that is, waiting until the spontaneous onset of labour or until a medical problem meant they needed to be induced. The study’s main outcome was caesarean delivery. Other outcomes included methods of delivery other than caesarean, birth complications and women’s experience of childbirth. The study was not designed to assess the effects of labour induction on stillbirth risk, which would need a much larger trial as these are still quite rare events.
The study took place at 39 NHS maternity units, so its results are relevant to all parts of the UK. It was well designed and conducted so the result is likely to be reliable.
What did it find?
- Induction of labour had no significant effect on the rate of caesarean deliveries (32%), compared with waiting for spontaneous labour (33%). Relative risk (RR) 0.99 (95% confidence interval [CI] 0.87 to 1.14)
- Induction of labour was not associated with differences in greater rate of interventions or other methods of delivery, with 38% of women in the induction group and 33% in the standard care group having delivery with the use of forceps or vacuum. RR 1.30 (95% CI 0.96 to 1.77)
- There was no difference between groups in the frequency of any harms to mother (such as heavy bleeding requiring blood transfusion) or baby (such as severe infection), or in the women’s experience of childbirth.
What does current guidance say on this issue?
There is no specific guidance on the issue of induction in older mothers.
NICE guidance on induction of labour says that women with uncomplicated pregnancies should usually be offered induction of labour between 41 and 42 weeks, to avoid the risks associated with prolonged pregnancy. The exact timing should take into account the woman's preferences and local circumstances.
NICE also points out healthcare professionals should talk to women being offered induction including the risks and benefits in specific circumstances and the proposed induction methods.
What are the implications?
Inducing labour at term in older mothers is already practised in the UK as it is thought to reduce stillbirth risk. This trial suggests that it does not increase the risk of caesarean section and is not associated with additional harm compared with spontaneous labour. However, as an editorial accompanying the research paper highlights; while the trial did not show evidence of harm, neither did it show evidence of benefit. So changing recommendations about the timing of delivery of uncomplicated pregnancies might be premature.
In particular, the study did not address the issue of whether induction at 39 weeks prevents stillbirth or affects other important outcomes. A larger trial looking at the effect of induction on stillbirth and other adverse events is currently being undertaken in the US, with a targeted enrolment of 6,000 women.
Citation and Funding
Walker KF, Bugg GJ, Macpherson M,et al. Randomized trial of labor induction in women 35 years of age or older. New Engl J of Med. 2016;374(9):813-22.
This project was funded by the National Institute for Health Research Research for Patient Benefit Programme (PB-PG-0610-22275).
Bibliography
Grobman W A. Editorial: Induction of labor and Cesarean delivery. N Engl J Med. 2016; 374:880-81.
NICE. Inducing Labour. CG70. London: National Institute for Health and Care Excellence London; 2008.
ONS. Birth summary tables, England and Wales: 2014. London: Office for National Statistics, 2015.
RCOG. Induction of labour at term in older mothers. Scientific impact paper no 34. London: Royal College of Obstetricians and Gynaecologists; 2013.
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