Women on weight loss medications like Ozempic and Mounjaro are finding themselves pregnant, despite in many cases being on birth control or previously having fertility issues.

On Facebook groups, TikTok and Reddit threads, women with “Ozempic babies” are gathering to share their stories, according to a report in USA Today. “I got pregnant on Ozempic and was on the pill! Baby boy is due in June,” one woman commented on a TikTok. While these pregnancies were unplanned or unexpected, for many of the women speaking out, it was a pleasant surprise.

32-year-old Deb Oliviara told USA Today that she fell pregnant two months after starting Ozempic, even though she was taking the pill at the time. As she had a history of fertility issues, she wasn’t concerned about getting pregnant. “We were open to the idea, but definitely not trying. It was very much a surprise and the only pregnancy, aside from my first, that didn’t come after a loss,“ she said. This is the sixth time she has been pregnant; she had previously experienced two miscarriages and one stillbirth. 

There are two reasons this might be happening. First, weight loss drugs, by correcting hormonal imbalances and metabolic disorders, can make people more fertile. But experts stress that people shouldn’t take them to get pregnant: while there hasn’t yet been research carried out with humans, studies involving animals suggest that these medications, if taken during pregnancy, can cause miscarriages and birth defects. It is recommended that women stop taking them at least two months prior to a planned pregnancy.

Second, some weight loss medications – like Mounjaro and Zepbound – are rendering oral contraception (the pill) ineffective. This is because they “delay gastric emptying”; in other words, the stomach takes longer to clean out, which has an impact on how medications are absorbed in the body. If the pill isn’t absorbed properly, then people may start ovulating again.

This effect is not as strong with drugs like WeGovy and Ozempic, but they do also affect how the stomach empties and there is still a chance they might make the pill less effective. An expert quoted in the USA Today article advised that people should use a backup form of contraception, like condoms.