Inducing labour at 41 weeks in low risk pregnancies is associated with a lower risk of newborn death compared with expectant management (a "wait and see" approach) until 42 weeks, suggests a trial published by The BMJ.
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."
Peer-reviewed? Yes (research); No (linked editorial)
Type of evidence: Randomised controlled trial; Opinion