Inducing Labor at 41 Weeks Lowers the Mortality Risks for Babies
Wed, April 21, 2021

Inducing Labor at 41 Weeks Lowers the Mortality Risks for Babies

Inducing labor at 41 weeks instead of 42 for late-term pregnancies has been found to significantly lower the risk of death in infants, according to the results of a new trial published in the British Medical Journal / Photo by: Halfpoint via Shutterstock

 

Inducing labor at 41 weeks instead of 42 for late-term pregnancies has been found to significantly lower the risk of death in infants, according to the results of a new trial published in the British Medical Journal.

The study investigated the risks of perinatal death in Sweden and compared it to the results of induction after 41 and 42 weeks of labor. There are doubts surrounding the best means to protect both the mother and the child during late-term pregnancies, but the results of the study may provide key information to making decisions in maternity care.

 

The Difference in Mortality Rates

From 2016 to 2018, 2,760 women were admitted to 14 hospitals for the study in which they were randomly assigned to either a 41-week or 42-week induction.

These women had low-risk, uncomplicated pregnancies that lasted for 41 weeks at the start of the study. In the group that received 41 weeks of induction, 86% underwent the method with a "wait and see approach" while 33% of the other group—dubbed as the "expectant management" group—needed induction if labor had still not occurred.

The results showed no difference in terms of women's health after childbirth, and the same could also be said for the proportions of cesareans and instrumental deliveries. Birth complications also only partly differed between the two groups: 33 in the induction group and 31 in the expectant management group.

However, there was a significant difference in terms of the number of infant deaths. Carrying out induction at 41 weeks didn't lead to any mortality, but foregoing to 42 weeks led to six cases of perinatal death as well as five stillborns and one death right after birth.

The researchers originally planned to recruit 10,000 women, but the study was immediately stopped following the results.

It is routine management for most Swedish birth centers to offer women the choice to induce labor at 40 weeks, according to Ulla-Britt Wennerholm, the lead author from Sahlgrenska University Hospital.

Wennerholm stated that they had to stop the study "for ethical reasons" because of the unexpected higher rate of perinatal death.

A Reasonable Option for Women

The researchers aimed to understand which method for inducing labor in late-term pregnancies would be safer for mothers and babies to make the best decisions in maternity care.

They investigated a composite of negative outcomes for the baby, which included stillbirth, neonatal death, brain hemorrhage, oxygen deprivation, difficulties in breathing, convulsions, and needed ventilation. Reuters says the researchers also looked at complications for mothers like cesarean delivery or vaginal birth with instruments, prolonged labor, use of epidural anesthesia, and hemorrhage.

"Neonatal mortality and morbidity, as well as maternal morbidity, increase when the pregnancy lasts more than 40 weeks, and the risks increase further as the pregnancy advances," said Wennerholm. "There is still uncertainty about obstetric management of late-term pregnancies and the optimal time to induce labor."

With the results of the study showing that the overall risk of an adverse outcome may be safer at 41 weeks of induction instead of 42, co-author Sara Kenyon said induction of labor at 41 weeks is a reasonable option for women. She noted that while pregnancies beyond 41 weeks are "usually safe and straightforward... there is a small yet significant increase in stillbirth risk past this."

Reuters says hospitals and birth centers now need to find a way to consider and implement this advice.

"Choice is important with maternity care, and clear information about available options should be accessible to all pregnant women, enabling them to make fully informed and timely decisions," said Kenyon. "We support the continual review of clinical guidelines as new evidence emerges to ensure best practice."

Taking Caution in Data Interpretation

If data from earlier work is combined with the results of this current study, senior author Henrik Hagberg said it will still show that inducing labor at 41 weeks will have lower mortality than starting labor at 42 weeks.

"What we’ve also shown in this study is that there don’t seem to be any medical disadvantages of induction at 41 weeks instead of 42," he added, noting that there was no increased risk of cesarean and instrumental deliveries in either method unlike what many had predicted.

Wennerholm said interpreting the results should be taken with caution. According to the lead author, the outcome may have been different if they were able to carry out with their original plan of a larger study. However, she noted that the pattern "would probably have been the same."

Shakila Thangaratinam, another lead author of the study, told health news site Healthline that their work is the largest of its kind that finally provided accurate estimates of possible risks of stillbirth in late-term pregnancies.

"Now that we understand the extent to which stillbirth risks increase with each week of pregnancy, we should be incorporating this information in all discussions around delivery plans in pregnant women at term."

The researchers aimed to understand which method for inducing labor in late-term pregnancies would be safer for mothers and babies to make the best decisions in maternity care / Photo by: Elnur via Shutterstock