Study links GLP-1 use to some pregnancy risks — but the study has key caveats
The use of Ozempic and similar drugs is not recommended during pregnancy, but stopping the drugs before conception may also carry some risks, new data suggests.
These data should be interpreted as an early signal that warrants further investigation, a researcher involved in the study told Live Science.
A poorly studied population
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, such as slowing digestion and changing the way the brain sends “hunger signals“Drugs have been linked to dozens of indirect benefitsincluding a lower risk of heart attack and dangerous blood clots.
But studies in mice and rabbits suggest that the drugs may increase risk of birth defects and miscarriages and restrict fetal growth. “So the current recommendation is to stop treatment before conception,” Maya said.
This recommendation means that a population of women stops using GLP-1 before pregnancy, raising the question of whether this may lead to negative effects. In the general population prescribed GLP-1, discontinuation of medications is accompanied by a rebound in weight gain and associated parameters, such as blood pressure, cholesterol and blood sugar. But these effects haven’t been studied much during pregnancy.
“To date, only one other study has examined gestational weight gain after GLP-1RA use” and “only a handful” have examined links between the drugs and other adverse pregnancy outcomes, according to epidemiologists. Carolyn Cesta, Jennifer Hutcheon And Kari Johansson written in a comment of new research.
To help fill this gap, researchers examined hundreds of singleton pregnancies delivered in the Mass General Brigham Health System between 2016 and 2025. They focused on approximately 450 pregnancies in which mothers used GLP-1 between three years before and 90 days after conception. About 50% stopped taking the medications within six months of conception, about 34% stopped taking the medication sooner, and 17% stopped after conception.
Just before pregnancy, the average BMI of these mothers were approximately 36 years old, which is classified as obese. The researchers compared these people treated with BPL to mothers who had never used these drugs but who also had a BMI of around 36 before pregnancy. The full range of BMIs in both groups was from “healthy” to “severely obese“, with similar proportions of people in each category and in each group.
Those who took and then stopped GLP-1 had an increased risk of premature birth, gestational diabetes and hypertensive disorders of pregnancysuch as gestational hypertension and preeclampsia, according to the analysis. Additionally, the GLP-1-treated group gained more weight during pregnancy – about 30 pounds (13.7 kilograms) on average, compared to an average of 23 pounds (10.5 kg) for the comparison group.
Notably, more people in the GLP-1-treated group had “excessive gestational weight gain,” which is associated with health risks for mother and baby. The amount of weight gain considered “excessive” varies based on the individual’s BMI before pregnancyaccording to the guidelines of National Academy of Medicine. About 65% of the BPL-treated group experienced “excessive” weight gain, compared to 49% of the control group.
Within the treated group, the timing of GLP-1 discontinuation did not appear to have a considerable effect on outcomes. “We expected, I think, a more pronounced change, but our results were quite similar,” Maya said. It may be that excess weight gain is the cause of the other observed pregnancy outcomes, but current data cannot demonstrate this with certainty, she noted.
Questions remain
An important limitation of the study was that the team compared people who had taken GLP-1 with people of similar body mass who had never taken it. In other words, the researchers looked at the treated group only after they had been exposed to GLP-1, when their BMI had likely fallen below their preprescription weight, the commentary authors noted.
In the future, researchers also want to take into account people’s pre-BPL weights and find a comparison group with comparable baseline BMIs, Maya said. This data, which they are currently working to gather, would help determine whether there are any benefits to using weight loss medications before conception, even if you then have to stop taking them during pregnancy.
The comment’s authors added that some of the new study’s findings appear to contradict other research. For example, some studies have established a link Use of GLP-1 to one lower risk of hypertensive disorders of pregnancy. But that may be because those previous studies included a higher proportion of people who were prescribed GLP-1 for diabetes, while the new study was geared toward people who were specifically taking obesity medications.
Like the new study, this earlier work compared GLP-1 users to “women with a similar BMI at the start of pregnancy but without a history of GLP-1RA use,” the commentary authors add. This could be common across studies due to “data gaps” in patient pre-treatment BMI databases and the difficulty of subsequently linking these BMI data to prescription and pregnancy records.
But these data gaps further highlight the need to study this population, because currently there is “limited, if any, clinical guidance” on the use of GLP-1 before conception, the commentary authors wrote. The new research, published Monday, November 24 in JAMAis starting to narrow the gap, but more studies are needed to understand the benefits and harms of medications for people planning to conceive.
“It is essential that we strive to generate the evidence needed to both inform obstetric care and guide treatment initiation decisions,” the commentary authors conclude.
As is often the case in drug research, the initial GLP-1 trials excluded people who said they wanted to conceive but were still using the drugs. “That’s how this research is happening,” Maya said, “and then slowly we step in and advocate for some of these vulnerable groups that weren’t included in the original studies.”
This article is for informational purposes only and is not intended to offer medical advice.
