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Induction at 41 weeks the safer option for women and their babies

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Inducing labour at 41 weeks in low risk pregnancies is associated with a lower risk of new-born death compared with expectant management (a “wait and see” approach) until 42 weeks, suggests a trial by researchers at Sahlgrenska Academy, Gothenburg University, Sahlgrenska University Hospital,  Karolinska Institutet, Karolinska University Hospital,  Örebro University and Uppsala University. Although the overall risk of death at 42 weeks is low, the researchers say induction of labour should be offered to women no later than 41 full weeks.

It is generally accepted that there is an increased risk of problems (“adverse perinatal outcomes”) for both mother and baby at or beyond 42 weeks of pregnancy. Some studies have suggested that inducing labour from 41 weeks onwards improves these outcomes, but there is no international consensus on how to manage healthy pregnancies lasting more than 41 weeks.

Current practice in the UK and Scandinavia is to induce delivery for all women who have not gone into labour by 42 weeks. So, researchers in Sweden set out to compare induction of labour at 41 weeks with expectant management until 42 weeks in low risk pregnancies.

The trial involved 2,760 women (average age 31 years) with an uncomplicated, single pregnancy recruited from 14 Swedish hospitals between 2016 and 2018. Women were randomly assigned to induction of labour at 41 weeks (1,381) or expectant management (1,379) until induction at 42 weeks if necessary.

The main outcome was a combined measure of babies’ health, including stillbirth or death in the first few days of life (known as perinatal death), Apgar score less than 7 at five minutes, low oxygen levels, and breathing problems. Other outcomes included admission to an intensive care baby unit, Apgar score less than 4 at five minutes, birth weight, pneumonia, or sepsis. Type of delivery and mothers’ health just after giving birth were also assessed.

For the main outcome measure, the researchers found no difference between the groups (2.4% of women in the induction group had an adverse perinatal outcome compared with 2.2% in the expectant management group). Other outcomes, such as caesarean sections and mothers’ health after giving birth, also did not differ between the groups. However, six babies in the expectant management group died compared with none in the induction group, and the trial was stopped early. The researchers estimate that, for every 230 women induced at 41 weeks, one perinatal death would be prevented.

They point to some limitations, such as differences in hospital policies and practices, that could have affected the results. But they say women with low risk pregnancies “should be informed of the risk profile of induction of labour versus expectant management and offered induction of labour no later than at 41 full weeks. This could be one (of few) interventions that reduces stillbirth,” they conclude.

This view is supported in a linked editorial by Professor Sara Kenyon and colleagues, who say induction at 41 weeks “looks like the safer option for women and their babies.” They stress that choice is important within maternity care, and say “clear information about available options should be accessible to all pregnant women, enabling them to make fully informed and timely decisions.”

Abstract
Objective: To evaluate if induction of labour at 41 weeks improves perinatal and maternal outcomes in women with a low risk pregnancy compared with expectant management and induction of labour at 42 weeks.
Design: Multicentre, open label, randomised controlled superiority trial.
Setting: 14 hospitals in Sweden, 2016-18.
Participants 2760 women with a low risk uncomplicated singleton pregnancy randomised (1:1) by the Swedish Pregnancy Register. 1381 women were assigned to the induction group and 1379 were assigned to the expectant management group.
Interventions: Induction of labour at 41 weeks and expectant management and induction of labour at 42 weeks.

Main outcome measures: The primary outcome was a composite perinatal outcome including one or more of stillbirth, neonatal mortality, Apgar score less than 7 at five minutes, pH less than 7.00 or metabolic acidosis (pH <7.05 and base deficit >12 mmol/L) in the umbilical artery, hypoxic ischaemic encephalopathy, intracranial haemorrhage, convulsions, meconium aspiration syndrome, mechanical ventilation within 72 hours, or obstetric brachial plexus injury. Primary analysis was by intention to treat.
Results: The study was stopped early owing to a significantly higher rate of perinatal mortality in the expectant management group. The composite primary perinatal outcome did not differ between the groups: 2.4% (33/1381) in the induction group and 2.2% (31/1379) in the expectant management group (relative risk 1.06, 95% confidence interval 0.65 to 1.73; P=0.90). No perinatal deaths occurred in the induction group but six (five stillbirths and one early neonatal death) occurred in the expectant management group (P=0.03). The proportion of caesarean delivery, instrumental vaginal delivery, or any major maternal morbidity did not differ between the groups.

Conclusions: This study comparing induction of labour at 41 weeks with expectant management and induction at 42 weeks does not show any significant difference in the primary composite adverse perinatal outcome. However, a reduction of the secondary outcome perinatal mortality is observed without increasing adverse maternal outcomes. Although these results should be interpreted cautiously, induction of labour ought to be offered to women no later than at 41 weeks and could be one (of few) interventions that reduces the rate of stillbirths.

Authors
Ulla-Britt Wennerholm, Sissel Saltvedt, Anna Wessberg, Marten Alkmark, Christina Bergh, Sophia Brismar Wendel, Helena Fadl, Maria Jonsson, Lars Ladfors, Verena Sengpiel, Jan Wesström, Göran Wennergren, Anna-Karin Wikström, Helen Elden, Olof Stephansson, Henrik Hagberg

BMJ material

BMJ abstract BMJ editorial

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