Tocolytic drugs after 30 weeks' gestation show no impact on baby health

Tocolytic drugs after 30 weeks' gestation show no impact on baby health | Image Credit: © RFBSIP - © RFBSIP - stock.adobe.com.

Baby health is not impacted by the use of tocolytic drugs after 30 weeks’ gestation in pregnant patients with increased preterm birth risk, according to a recent study published in The Lancet.¹

Understanding preterm birth and its risks

Preterm birth occurs in 1 in 10 pregnancies, increasing the risk of severe short- and long-term morbidity and mortality among infants. This has led to tocolytic drug use after 24 weeks’ gestation and before 34 weeks’ gestation as a standardized treatment among pregnant women with increased preterm birth risk to prolong pregnancy.¹

"Whether prolongation of pregnancy by using tocolytic drugs actually benefits the health of the baby has not been substantiated by research until now," said Martijn Oudijk, professor of prevention and treatment of premature birth at Amsterdam UMC.¹

Advances in preterm birth detection

Detecting and treating preterm birth has been linked to decreased neonatal morbidity and mortality.² A 2024 study found reduced complications when using the PreTRM test prevention strategy to predict preterm birth risk. This blood-based biomarker test evaluated proteins in the blood linked to preterm birth, improving risk prediction.

The PreTRM test may be used for risk prediction in patients between 18- and 20-weeks’ gestation. In the trial of adult pregnant patients, significant reductions in neonatal morbidity and mortality were observed. These included reduced hospital and neonatal intensive care unit length of stay, and reduced risks of preterm birth and spontaneous preterm birth.³

Study on tocolytics and neonatal outcomes

Investigators conducted an international, multicentre, randomised, double-blind, superiority trial across 26 hospitals in the Netherlands, England, and Ireland to evaluate the impact of tocolytics on neonatal outcomes.³ Participants included women aged at least 18 years with singleton or twin pregnancy at risk of preterm birth from 30 to 33 weeks’ gestation.

These patients were randomly assigned 1:1 to receive either intravenous atosiban or placebo. Co-primary outcomes included perinatal mortality, defined as stillbirth or death through 28 days’ postpartum, and 6 severe neonatal morbidities.³

Study findings and key results

There were 752 participants included in the intention-to-treat analysis, 375 of whom were assigned to the atosiban group and 377 to the placebo group. Eight percent and 9% of these patients, respectively, reported a primary outcome, with infant death occurring in 0.7% and 0.9%, respectively.³

This indicated a relative risk of 0.73 for infant death, highlighting no significant difference. Additionally, no cases of infant death were linked to the study drug. There were also no significant differences in maternal adverse events between groups, and no cases of maternal death were reported.³

Conclusion

These results indicated no superiority from atosiban over placebo for improving neonatal outcomes among patients with increased preterm birth risk. Investigators recommended reducing practice variation across countries and providing evidence-based treatment to patients at risk of preterm birth.³

"The purpose of delaying childbirth is to give newborns a better start and improve their health,” said Oudijk.¹ “Premature birth often has a medical cause, such as an infection or problems with the placenta. A prolonged stay in the uterus longer might actually be harmful."

References

1. Contraction inhibitors after 30 weeks have no effect on baby's health. Amsterdam University Medical Center. March 3, 2025. Accessed March 4, 2025. https://www.eurekalert.org/news-releases/1075021
2. Krewson C. PreTRM test shows efficacy in reducing severe neonatal morbidity and mortality. Contemporary OB/GYN. July 18, 2024. Accessed March 4, 2025. https://www.contemporaryobgyn.net/view/pretrm-test-shows-efficacy-in-reducing-severe-neonatal-morbidity-and-mortality
3. I van der Windt L, Klumper J, Duijnhoven RG, et al. Atosiban versus placebo for threatened preterm birth (APOSTEL 8): a multicentre, randomised controlled trial. The Lancet. 2025. doi:10.1016/S0140-6736(25)00295-8