Study links GLP-1 use to pregnancy risk, but the study comes with important caveats.

Ozempic and similar drugs are not recommended for use during pregnancy, but new data suggests that stopping the drug before pregnancy may carry some risks.

These data should be interpreted as an early signal that warrants further investigation, researchers involved in the study told Live Science.

This analysis had important limitations. Women who used weight management drugs and those who did not may not have been completely comparable, and the study was not designed to capture the potential benefits of taking Ozempic or similar drugs before pregnancy.

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“We don’t know if there are benefits or increased risks if you get pregnant at a low birth weight and then go off the medication,” said the study’s lead author, Dr. Jacqueline Maya, a pediatric endocrinologist and physician-researcher at Massachusetts General Hospital who studies how events during pregnancy affect the health of both mother and child.

For now, Maya said the new findings are a “cautionary warning” for doctors. “We just need to monitor [these patients] There were some obstetric outcomes that we needed to monitor, so keep a close eye on it,” she told Live Science.

Understudied populations

Drugs like Ozempic, Wegovy, and Zepbound are “glucagon-like peptide-1 receptor agonists,” or GLP-1 for short. GLP-1 regulates weight and improves blood sugar levels through several mechanisms, including slowing digestion and changing the way the brain sends “hunger signals.” These drugs have been linked to dozens of knock-on effects, including a lower risk of both heart attacks and dangerous blood clots.

However, studies in mice and rabbits suggest that the drug may increase the risk of birth defects and miscarriage, and limit fetal growth. “So the current recommendation is to stop the drug before pregnancy,” Maya said.

This recommendation means that many women will stop using GLP-1 before pregnancy, raising questions about whether it may cause any adverse effects. In the general population prescribed GLP-1, discontinuation of the drug causes weight gain and a rebound in related indicators such as blood pressure, cholesterol, and blood sugar levels. However, these effects during pregnancy are less studied.

In a commentary on the new study, epidemiologists Carolyn Sesta, Jennifer Hutcheon, and Kari Johansson write that “only one other study to date has examined pregnancy weight gain after GLP-1RA use,” and only “a handful” of studies have looked at associations between the drugs and other adverse pregnancy outcomes.

To fill this gap, researchers looked back at hundreds of singleton pregnancies delivered at Brigham General Hospital in Massachusetts between 2016 and 2025. They focused on about 450 pregnancies in which mothers used GLP-1 from three years before pregnancy to 90 days after pregnancy. About 50% stopped taking the drug within 6 months of pregnancy, about 34% stopped sooner, and 17% stopped after pregnancy.

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Just before pregnancy, these mothers had an average BMI of about 36, which would classify them as obese. Researchers compared these GLP-treated people to mothers who had never used the drug but had a pre-pregnancy BMI of about 36. The full range of BMI for both groups was from ‘healthy’ to ‘severely obese’, with similar proportions of people in each category in each group.

The analysis found that people who took GLP-1 and then discontinued it had an increased risk of preterm birth, gestational diabetes, gestational hypertension, and pre-eclampsia. Additionally, the GLP-1 treatment group gained more weight during pregnancy, gaining an average of about 30 pounds (13.7 kg) compared to an average of 23 pounds (10.5 kg) in the comparison group.

And of note, more people in the GLP-1 treatment group suffered from “excessive gestational weight gain,” which is associated with health risks for both mother and baby. According to guidelines from the National Academy of Medicine, the amount of weight gain that is considered “excessive” depends on an individual’s pre-pregnancy BMI. About 65% of the GLP-treated group had “excess” weight gain, compared to 49% of the comparison group.

Within the treatment group, the timing of GLP-1 cessation did not appear to significantly influence the outcome. “I think we expected a more noticeable change, but the results were about the same,” Maya said. Excess weight gain may have caused the other pregnancy outcomes observed, but current data cannot prove that with certainty, she noted.

doubts remain

One significant limitation of the study was that the researchers compared people who took GLP-1 to people of similar weight who had never taken the drug. In other words, the researchers observed the treatment group only after exposure to GLP-1, when their BMI was likely lower than their pre-prescription weight, the commentary authors noted.

In the future, researchers hope to also take people’s pre-GLP weight into account and find a comparison group with a similar baseline BMI, Maya said. These data that they are currently working on collecting will help put into context whether there is any benefit to using drugs to lose weight before pregnancy, even if the drug must be stopped during pregnancy.

The authors of the commentary added that some of the new study’s findings appear to contradict other studies. For example, some studies have linked the use of GLP-1 to a reduced risk of gestational hypertension. However, that may be because these previous studies had a higher proportion of people prescribed GLP-1 for diabetes, whereas the new study was biased toward people who took the drug specifically for obesity.

Similar to the new study, this previous study compared GLP-1 users to “women with a BMI close to that of early pregnancy but without a history of GLP-1RA use,” the authors added. This may be common to all studies due to the fact that databases are “data deficient” on patients’ pre-treatment BMI, and it is difficult to subsequently link that BMI data to prescriptions or pregnancy records.

However, these data gaps further emphasize the need to study this population, as there is currently “limited or no clinical guidance” regarding the use of GLP-1 before pregnancy, the commentary authors write. A new study published Monday (Nov. 24) in the journal JAMA begins to fill that gap, but more research is needed to understand the drug’s pros and cons for people planning pregnancy.

“It is important to strive to generate the evidence necessary to inform obstetric care and guide decisions to initiate treatment,” the commentary authors concluded.

As is common in drug research, GLP-1’s initial trial excluded people who said they were planning a pregnancy, but those people still use these drugs. “This is how this study unfolds,” Maya said, “and slowly we become advocates for some of the vulnerable populations that were not included in the original study.”