Research suggests inducing labour at 41 weeks reduces risk, says maternity expert

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A University of Birmingham maternity expert says research indicates that inducing women with low-risk pregnancies at 41 weeks rather than waiting until 42 weeks reduces risk to their baby’s life.

Current practice in the UK and Scandinavia is to induce delivery for women who have not gone into labour by 42 weeks. Sara Kenyon, Professor of Evidence Based Maternity Care at the University of Birmingham’s Institute of Applied Health Research, has co-authored an editorial published in the BMJ focussed on a paper establishing the optimal time to induce women who have gone beyond 40 weeks of pregnancy.

The paper details the most recent trial, the results of which are published in The BMJ, and saw researchers in Sweden compare induction of labour at 41 weeks with "expectant management" until induction at 42 weeks for those who had not given birth.

Called the SWEdish Post-term Induction Study (SWEPIS), the trial involved 2,760 women with an uncomplicated, single pregnancy who were admitted to 14 Swedish hospitals between 2016 and 2018.

The researchers measured for a ‘primary composite outcome’, including stillbirth, death in the first few days of life, low oxygen levels, and breathing problems). While overall there was no difference between the groups in the numbers of babies with these problems, six babies in the ‘expectant management’ group died compared with none in the group induced at 41 weeks, so the trial was stopped early. These were five stillbirths and one early neonatal death. Fewer babies in the group induced at 41 weeks were admitted to a neonatal intensive care unit.

The researchers estimate that, for every 230 women induced at 41 weeks, one perinatal death would be prevented.

Although the authors say differences in hospital policies and practices could have affected the results, they recommend that women with low-risk pregnancies should be offered inductions "no later" than at 41 weeks and that "this could be one of few interventions that reduces stillbirth".

In a linked editorial, Professor Kenyon and colleagues say induction at 41 weeks "looks like the safer option for women and their babies".

Professor Kenyon adds: "The findings of this Swedish trial add to what is already known and suggest that while pregnancies that continue to 42 weeks are usually safe and straightforward, there is a small yet significant increase in the risk of neonatal death after 41 weeks.

"Current UK guidance recommends that induction of labour should be offered to women with uncomplicated pregnancies by 42 weeks to avoid the known risks of prolonged pregnancy, including stillbirth.

"We support the continual review of clinical guidelines as new evidence emerges to ensure best practice.

“It’s important that a woman’s individual needs and preferences should always be taken into account and they must have the opportunity to make informed decisions in partnership with their healthcare professionals.”

The editorial was co-authored by Mr Lee Middleton, a senior statistician at the University of Birmingham’s Clinical Trials Unit, Dr Magdalena Skrybant, also of the University of Birmingham, and Tracey Johnston, consultant in fetal maternal medicine at Birmingham Women’s and Children’s NHS Foundation Trust.

They added: "Choice is important within maternity care, and clear information about available options should be accessible to all pregnant women, enabling them to make fully informed and timely decisions. The challenge for maternity services is implementation."

Notes to Editors:

  • Journalists can request interviews via Emma McKinney, Communications Manager (Health Sciences), University of Birmingham, tel: +44 (0) 121 414 6681, or contact the press office on +44 (0) 7789 921 165.
  • The University of Birmingham is ranked amongst the world’s top 100 institutions. Its work brings people from across the world to Birmingham, including researchers, teachers and more than 6,500 international students from over 150 countries.
  • In May 2019, Professor Sara Kenyon received a prestigious Royal College of Midwives Fellowship for her contribution to midwifery, an honour given to just a handful of midwives each year. Professor Kenyon qualified as a midwife in 1982 and has been a trailblazer throughout her career. She was among the very first midwives in the UK to perform ultrasounds scans of women in pregnancy, and helped develop a scanning course for midwives. She was involved in the beginnings of the support group ‘Antenatal Results and Choices’ and then went on to lead the ORACLE trial and Children Study which has transformed antibiotic use in preterm birth. Professor Kenyon leads a West Midlands-based project, which has developed a maternity triage system and training for midwives to standardise their discussion with women about where they want to give birth. She is also leading research looking at the use of the drug Oxytocin in delayed and induced labour and links to caesarean section rates. She is a midwife on 'MBRRACE-UK', a group investigating maternal and infant deaths and stillbirths. This is a project that reviews all deaths of mothers and babies around pregnancy and makes recommendations to reduce them. She is also involved in the Perinatal Mortality Review Tool which is working to standardise how the deaths of babies during and after pregnancy are reviewed. She co-chairs the Perinatal Confidential Enquiries.
  • Wennerholm et al (2019). ‘Induction of labour at 41 weeks versus expectant management until 42 weeks (Swedish post-term induction study, SWEPIS): multicentre, open label, randomised superiority trial’. The BMJ. DOI: 10.1136/bmj.l6131. 
  • Kenyon et al (2019). ‘When to induce late term pregnancies’. The BMJ. DOI: 10.1136/bmj.l6486.