A nationwide Danish registry study covering more than 750,000 pregnancies found that accidental GLP-1 exposure around conception was associated with preterm birth only when the drug had been prescribed for existing diabetes, not for weight management.

The medications were semaglutide (sold as Ozempic and Wegovy) and liraglutide (Saxenda), both GLP-1 receptor agonists, originally developed for type 2 diabetes and now widely prescribed for weight loss because they suppress appetite. Their safety in pregnancy has not been established, and the researchers say current advice to stop eight weeks before trying to conceive rests on early model-organism work rather than real-world data.

Key results

The team examined 756,636 single-baby pregnancies among 480,231 women delivering between October 2009 and December 2023, classifying a pregnancy as exposed if a prescription was filled in the eight weeks before or after the last menstrual period. That window caught 529 pregnancies.

After adjusting for maternal age, BMI, smoking, education, region, pre-existing diabetes and calendar time, most of the initial associations disappeared. What remained was preterm delivery among women prescribed the drugs for diabetes: adjusted odds 70 percent higher for liraglutide and 84 percent higher for semaglutide, compared with unexposed women. No significant association with preterm birth or the other complications studied appeared in the weight-management group.

Why the indication matters

This is the useful part, and it is the kind of distinction most GLP-1 pregnancy coverage flattens. Lead author Professor Henriette Svarre Nielsen said future studies must account for why a drug was prescribed, since combining the two groups can hide real differences in underlying health. First author Dr. Kathrine Hviid said the pattern suggests diabetes itself, rather than the medication, may be driving the association.

An invited commentary from Kaiser Permanente researchers Yeyi Zhu and Monique Hedderson called the results a complement to an emerging evidence base on GLP-1 reproductive safety.

Limitations

The study was observational and cannot establish that the medications caused preterm births. Exposure was inferred from filled prescriptions, not confirmed use, though the authors argue high cost makes compliance likely.

Bottom line

Nielsen said the findings do not justify abandoning current guidance to stop these drugs before a planned pregnancy, and they do not establish that the medications are safe during pregnancy. The question of how to counsel women exposed by accident remains open.