Controversial pregnancy trial identifies safer induction cut-off date
The results of a Swedish trial investigating the best practice for managing late-term pregnancies have finally been published, recommending women induce labor no later than week 41 of gestation. The study was controversially halted late in 2018 after a number of perinatal deaths raised ethical issues.
Called the Swedish post-term induction study (SWEPIS), the trial spanned 14 hospitals in the country. The ultimate goal was to track 10,000 healthy expectant women, recruited at week 40 of their pregnancies. Once enrolled, the subjects were randomly assigned into two groups. One group had their labor induced at week 41, while the other group held off for a natural birth, or an induction at week 42.
In October 2018 the trial was suddenly halted after it was reported there were six perinatal deaths recorded in the late induction group. By this point in the trial only 2,760 women had been recruited, a little over a quarter of the planned cohort. All six perinatal deaths (five stillbirths and one early neonatal death) had occurred in the late induction group who were holding off until at least week 42.
General recommendations for late-term pregnancies currently vary from country to country. The World Health Organization recommends birth be induced at week 41 of gestation, while current practice in many places from the UK to Scandinavia will hold off until week 42 before pressing for induction.
Perinatal mortality was not the primary outcome of the SWEPIS trial. Instead, the researchers were more interested in evaluating general adverse outcomes for mother and baby. A composite outcome score was generated for each subject, incorporating factors such as birth-weight and the health of mother and child. Interestingly, the published data concludes there was little difference seen on this primary measure between the two cohorts.
It was the striking mortality rate in the week 42 cohort that guided much of the study’s ultimate conclusions. The researchers noted in the study’s conclusion, there was little to no adverse effect seen in inducing birth at week 41, so considering the heightened risk of stillbirth related to longer gestation the ultimate recommendation from the research was clear.
“Although these results should be interpreted cautiously,” the researchers write in the published paper, “induction of labor 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.”
Despite the study’s abrupt discontinuation, experts are hailing the rigor and design of the research. Kasia Maksym, from University College London’s Institute for Women’s Health, calls the study “important” with a “nearly perfect design.”
“There is potential for data to be biased as recruitment was stopped before reaching planned target," notes Maksym, who did not work on the new research. “However, it was stopped for the reason, the very reason this study was designed for – to answer the question: which management is the safest in prolonged pregnancy. The result is not unexpected. The message is clear: there is an intervention, which can reduce risk of perinatal mortality in prolonged pregnancy, without additional risk for mother and baby.”
Sarah Stock, from the University of Edinburgh, says this new research adds to a growing body of evidence affirming the safety of inducing labor by week 41 of gestation. Stock notes the Swedish data validates the safety profile of induction at week 41 compared the common “wait and see” approach.
“Other benefits of induction at 41 weeks included fewer babies separated from their mothers because of admission to specialist neonatal care, fewer babies with high birth weight, and fewer babies with complications like jaundice,” Stock says.
The new study was published in the journal The BMJ.