Anti-contraction drug does not appear to also reduce poor neonatal outcomes

The use of the anti-contraction (tocolytic) drug atosiban in cases of threatened premature birth after 30 weeks of pregnancy is not more effective than placebo at reducing poor neonatal outcomes. researchers reported on March 3, 2025  in The Lancet.

Tocolytic drugs are standard treatment for women who appear to be giving birth prematurely, after 24 weeks and before 34 weeks of gestation.

The rationale for their use has been that prolongation of pregnancy allows the fetus more time to develop, thereby decreasing the likelihood of health problems.

“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 University Medical Center (UMC) in the Netherlands. “We have to ask ourselves whether tocolytic drugs should continue to be a standard treatment for TPL after 30 weeks of pregnancy,” he added,

This international, randomized, double-blind trial enrolled subjects at hospitals in The Netherlands, England and Ireland.

Women with a singleton or twin pregnancy with threatened preterm birth after 24 weeks and before 34 weeks of gestation were randomized to intravenous atosiban or placebo.

The primary outcome was a composite of neonatal mortality and six severe morbidities.

Between December 4, 2017 and July 24, 2023 a total of 755 subjects were randomized to treatment, and 752 were included in the final analysis of data.

The primary outcome occurred in 37/449 (8.2%) of the infants in the atosiban group and 40/435 (9.2%) in the placebo group. There were three (0.7%) and four (0.9%) deaths respectively, and they did not appear to be related to the study drug.

Adverse events among the mothers did not differ between the study groups.

“We did not demonstrate superiority of atosiban over placebo in improving neonatal outcomes  as treatment for threatened preterm birth from 30 +0 through 33 +6 weeks of gestation,” the authors concluded.

“This is the largest placebo-controlled study ever performed investigating the effects of tocolytic drugs on the baby’s health.” added Amsterdam UMC PhD-student Larissa van der Windt. “Our results showed no difference whatsoever. There was no benefit but also no harm done,”