When pregnant women have not delivered by around 41 weeks, their babies are slightly less likely to have serious complications if labour is induced instead of letting nature take its course, a Dutch study suggests.
Researchers randomly assigned 1,801 healthy women who were 41 weeks pregnant either to have labour induced or to receive so-called expectant management, with an induction if needed by 42 weeks.
Overall, 1.7 per cent of women who were induced at 41 weeks had babies with serious complications, compared with 3.1 per cent of mothers in the expectant management group, researchers report in The BMJ.
"Most pregnancies have a good outcome with both strategies, with a small difference in the risk of adverse perinatal outcomes favouring induction of labour," said senior study author Dr. Esteriek de Miranda of the University of Amsterdam.
"The absolute risk of severe adverse outcome is low, which justifies women's choice for either policy," de Miranda said by email.
Pregnancy normally lasts about 40 weeks, and babies born after 37 weeks are considered full term. The current study focused on late-term pregnancies between 41 and 42 weeks.
The World Health Organisation recommends labour induction at 42 weeks because allowing women to continue pregnancies longer is associated with an increased risk of death and complications for both mothers and babies. But previous research on the difference in outcomes between 41 and 42 weeks' gestation has been mixed, and guidelines in many countries differ on which of these approaches is best.
There was one stillbirth in the induction group and two with expectant management, the study found.
With induction at 41 weeks, three babies were admitted to the NICU, compared to eight in the expectant management group.
In the earlier induction group, fewer babies had low Apgar scores, an assessment of wellbeing that examines things like breathing and pulse shortly after birth.
Eleven babies in the induction group and 23 in the expectant management group had Apgar scores low enough to indicate they needed urgent medical attention.
No babies induced at 41 weeks and three who arrived later had Apgar scores so low they indicated the potential for serious health impairments.
Expectant management until 42 weeks is the current standard of care for women with low-risk pregnancies in the Netherlands. The goal of the study was to show whether expectant management was worse than induction at 41 weeks, and the study didn't find a big enough difference in outcomes to support this conclusion, the authors note.
Larger trials would also be needed to evaluate differences between induction and expectant management for many serious but rare complications for mothers and babies, the researchers write.
"We don't know when induction of labour should be offered between 41 and 42 weeks and the results of this trial do not mean we have enough information to make any recommendation about that," said the coauthor of an accompanying editorial, Dr. Tracey Johnston of Birmingham Women's and Children's NHS Foundation Trust in the UK.
"The take-home message for women is that many factors need to be considered when thinking about induction of labour, and that this should be discussed in detail with their health professional, who should discuss the risks and benefits for both mother and baby taking into account their individual circumstances to facilitate the woman making a properly informed choice," Johnston said by email.