As semaglutide, a drug used to treat diabetes and weight loss, continues to grow in popularity, health experts are highlighting an overlooked, but potentially serious side effect of the drug: an increased risk of miscarriage and birth defects in pregnant individuals, Julia Belluz writes for Vox.

A lesser-known risk of semaglutide

Semaglutide, a drug that mimics a  hormone  called glucagon-like peptide-1 (GLP-1) to target areas of the brain that regulate appetite and food intake, has grown in popularity in recent months as an effective weight-loss treatment. The drug, which is made by  Novo Nordisk, is available in two forms: Ozempic, a diabetes treatment, and Wegovy, a higher dose of the drug approved for weight loss.

As more people use semaglutide, there have been a growing number of reports of potential side effects. For example, some people have reported  experiencing "Ozempic face," a result of rapid weight loss that makes the face look deflated and appear older. Some consumers and experts have also raised concerns about unintended muscle loss after using the drug.

Now, another potential risk of semaglutide has emerged. According to  FDA, it is recommended that people discontinue use of Ozempic and Wegovy at least two months before getting pregnant due to potential risks of miscarriage and birth defects. For people using Ozempic to treat diabetes, the drug's label says that patients may continue the drug "only if the potential benefit justifies the potential risk to the fetus."

Currently, semaglutide is not being tested in pregnant individuals, but animal studies found that rats, rabbits, and monkeys who were treated with the drug had higher rates of miscarriage. Their offspring were also smaller and had more birth defects than what would normally be expected.

So far, it's not clear whether these birth complications were due to weight loss from semaglutide or the medication itself. "During a period of rapid growth, if the fetus is in a caloric deficit and the mother is in a caloric deficit, that will clearly produce some impairment of fetal growth," said Daniel Drucker, a scientist and endocrinologist at the  University of Toronto  who helped discover GLP-1.

According to an FDA spokesperson, the agency believes the pregnancy complications observed in animals taking semaglutide were likely caused by weight loss and poor nutrition. The spokesperson added that the agency is "unaware of any humans harmed during pregnancy or in utero because of semaglutide exposure," Belluz writes.

Still, based on the animal studies, "taking semaglutide during pregnancy may increase the risk of birth defects and miscarriage above background for the US general population," the spokesperson said, the extent of the risk is still unknown.

Currently, Novo Nordisk, at FDA's request, is organizing a study to analyze potential complications related to Wegovy in pregnancies that have already occurred. The company has also created a registry to prospectively follow health outcomes in individuals exposed to Wegovy during pregnancy compared to those who were not. The first study is expected to be completed in 2027 while the second study will be completed in 2033.

Health experts encourage increased awareness of these risks

Although there are warnings about potential pregnancy issues for both Ozempic and Wegovy, health experts say they are not displayed prominently in either the drug labels or side-of-package warnings and could be easily missed. In addition, some people may be prescribed the drug for off-label use, meaning that their physicians may be less familiar with potential side effects.

"My guess is most physicians don't know the concerns," said Joseph Ross, a professor at  Yale School of Medicine. Some patients may also be getting unregulated forms of semaglutide online  on their own, either from other countries or compounding pharmacies, making it even harder for them to learn about potential issues with the drug.

In general, Ross said that "widespread educational efforts are needed as a precaution." Some ways to raise awareness would be through public information campaigns or extra messaging in the drug's marketing materials, including its labels, ads, and packaging.

"This pregnancy issue is a real issue. There's no question about it," Drucker said. "The drug manufacturers and most certainly prescribing health care providers should highlight this issue to [people] with potential for pregnancy."

Similarly, an obesity researcher who is associated with Novo Nordisk said that "[g]iven the majority of people accessing these medications are women, and a significant portion will be of childbearing age, this needs more attention."

"If a pregnant woman is taking these drugs and doesn't realize the risks, and it does bear out the drugs cause human fetal harm, we could end up in an awful mess — pregnancies ending in miscarriage or neonates born with birth defects," Ross said. (Belluz, Vox, 4/18)