New research suggests the risks tied to early pregnancy exposure to popular weight loss drugs may not be the same for every patient.
New research suggests that early pregnancy exposure to popular weight loss drugs may not carry the same risks for every patient.
These medications were linked to a higher risk of preterm birth among women who accidentally took them shortly before or during early pregnancy to manage pre-existing diabetes.
But in a large study of more than 750,000 pregnancies, researchers found no connection to preterm birth or other obstetric complications when the drugs were used for weight loss.
The study, published in Human Reproduction Open, one of the world’s leading reproductive medicine journals, suggests that diabetes itself, rather than the drugs alone, may help explain the higher risk of preterm birth.
Drugs such as semaglutide (brand names: Ozempic, Wegovy) and liraglutide (Saxenda) are part of a class of medications known as GLP-1 receptor agonists (GLP-1 RAs). They were originally developed to treat type 2 diabetes. Because they reduce appetite, they were also found to help people lose weight. However, there is no evidence showing they are safe to use during pregnancy.
Professor Henriette Svarre Nielsen, from the Department of Gynecology and Obstetrics at Copenhagen University Hospital Hvidovre, Hvidovre, Denmark, who led the study, said: “GLP-1 RA treatment has, within the last few years, become the medication with the sharpest increase in prescription worldwide. Current guidance suggests the treatment should be stopped eight weeks prior to planning a pregnancy. However, this is based on early-phase model organism studies, and not real-world evidence. Nonetheless, because of its widespread adoption, inadvertent exposure in early pregnancy is inevitable, and there is hardly any evidence to guide clinical counseling when it happens.”
How the researchers conducted the study
The team examined whether accidental GLP-1 RA use during the periconceptional period was linked to complications such as preterm birth (birth before 37 weeks), preeclampsia, gestational diabetes, giving birth to a child large for gestational age, stillbirth, and problems with the placenta.
They analyzed data from Danish nationwide health registries covering 756,636 singleton pregnancies among 480,231 women that ended in delivery between October 1, 2009, and December 31, 2023. A pregnancy was considered inadvertently exposed if the woman redeemed a prescription for liraglutide or semaglutide within eight weeks before or after the date of her last menstrual period. This 16-week window covered the time when a woman might not yet know she was pregnant, as well as the early stages of embryonic organ development. In total, 529 pregnancies were exposed to GLP-1 RAs during the periconceptional period.
The researchers adjusted the results for the mothers’ age, body mass index (BMI), smoking status, geographic region, education, pre-existing diabetes, and the month and year of pregnancy to account for seasonal and other trends.
The first author of the paper, Dr Kathrine Hviid, a PhD student in the same department, said: “We made some extremely important findings that have implications for future studies, such as randomized controlled trials of GLP-1 RA usage in pregnancy, and for clinical counseling.
“We found that these medications were associated with an increased risk of preterm birth, but the risk was only present when the medication was used for diabetes treatment, and not for weight management. This suggests that the underlying condition of diabetes, rather than the medication, may be driving this association.”
Differences between diabetes treatment and weight management
The researchers found higher rates of several obstetric complications among women who took GLP-1 RAs. But after adjusting for factors that could influence the results, they found only one remaining increase: a higher risk of preterm birth among women who had taken liraglutide or semaglutide for diabetes treatment.
Compared with women who did not take GLP-1 RAs, the risk was 70% higher for liraglutide and 84% higher for semaglutide. Among women with pre-existing diabetes taking semaglutide, the drug was associated with an approximately 11% risk of preterm birth. For liraglutide, the risk was about 9%.
Prof. Nielsen said: “Future studies must take account of the reason a woman has been prescribed these medications, as the risks differ between women using GLP-1 RAs for diabetes versus weight management. This is one of the first studies to examine GLP-1 RA exposure in early pregnancy according to the reason for prescription. As more evidence accumulates, these findings will guide clinical counseling for women inadvertently exposed to GLP-1 RAs in early pregnancy. In Denmark, about 70% of people who use weight loss medications are women and so it is inevitable that some may take it without realizing they are pregnant.”
However, she said more research is needed, and it is still too early to change the recommendation that GLP-1 RAs should be stopped before pregnancy, or to change counseling based on the reason the drugs were prescribed.
Strengths, limitations, and clinical perspective
A major strength of the study is its size. But the findings cannot show that GLP-1 RAs cause preterm birth, only that they are associated with it. The researchers also had no direct data confirming that women actually took the medications after filling their prescriptions. Still, in Denmark, patients must pay for GLP-1 RA injections, although the government provides a subsidy when they are prescribed for diabetes treatment. For example, a 1 mg (0.000035 oz) injection of Wegovy or Ozempic (semaglutide) costs about €180 and €114, respectively, including the subsidy for diabetes treatment.
Dr Hviid said: “Because of the high cost, we assume that compliance is very high among the women prescribed GLP-1 RAs.”
In an invited commentary accompanying the paper, Drs Yeyi Zhu and Monique Hedderson, from Kaiser Permanente Northern California and the Center for Upstream Prevention of Adiposity and Diabetes Mellitus, in Pleasanton, California, USA, write that the study’s findings “complement and extend an emerging evidence base on the reproductive safety of GLP-1 RAs.”
They continue: “For clinicians, the study by Hviid et al (2026) may inform preconception and early pregnancy counseling. The observation that elevated preterm birth risk was confined to women treated for diabetes, and not to those using GLP-1 receptor agonists for weight management, supports more balanced, individualized discussions with patients who may have experienced inadvertent periconceptional exposure. For patients with diabetes, the study reinforces the importance of recognizing diabetes as an important risk factor for obstetric complications and prioritizing metabolic health and glycemic management before and during pregnancy.”
References: “Periconceptional GLP-1 receptor agonist exposure and obstetric outcomes: a Danish nationwide cohort study” by Kathrine Vauvert R Hviid, Karina Banasik, Laust Hvas Mortensen, Sten Madsbad, Katrine Strandberg-Larsen, Nina Rica Wium Geiker, David Westergaard and Henriette Svarre Nielsen, 18 March 2026, Human Reproduction Open.
DOI: 10.1093/hropen/hoag015
“When drugs meet disease: disentangling diabetes, obesity, and periconceptional GLP-1 receptor agonist safety” by Yeyi Zhu and Monique M Hedderson, 18 March 2026, Human Reproduction Open.
DOI: 10.1093/hropen/hoag016
Funding: Novo Nordisk Foundation, AP Moller Foundation, NordForsk, Villum Foundation, Independent Research Fund Denmark and Centre for Childhood Health
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