Weighing Risks, Benefits, and Unknowns
Early looks at small human data sets, mostly involving semaglutide and earlier short-acting GLP-1s, and their impact on the risk for birth defects are “reassuring,” Boots said.
“But birth defects are just one small aspect. There’s also metabolic health and things like that long-term. Understanding what it does to the growing baby and the proximity of that medication to that growing baby is really important to see, and can’t be answered with animal studies, not perfectly anyway,” Boots said.
There are no published reports, from clinical trials nor case collections, examining the use of tirzepatide among pregnant people.
“One of the most important questions we need to answer is the preconception safety of these medications, and that includes safety for men,” Joshua Halpern, MD, MS, an adjunct assistant professor of urology at Northwestern University’s Feinberg School of Medicine, and chief scientific officer for Posterity Health, said in an email to this news organization.
“For example, a recent study found that men who were taking metformin, another popular medication for diabetes, were more likely to have children with birth defects, compared with those who were not taking the medication,” Halpern said. “Further studies are needed to determine whether a similar effect might hold true for the GLP-1 agonists.”
Small early studies on sperm are encouraging, Halpern said, suggesting that GLP-1 use may be beneficial, but a better understanding of direct effects is needed.
Among women, there may be cases where continuing use of a GLP-1 during pregnancy may offer benefits that outweigh risks, Boots suggested. Manufacturers have also created pregnancy exposure registries to measure the safety of their therapies during pregnancy.
“I have a group of patients whose sugars are so well controlled on these medications, but as soon as they come off, they get weight regain and their glucose is just so poorly controlled,” she said. “There may be a group of women where the benefits of glucose control outweigh the risks of being on the medication the whole pregnancy.”
The list of important unknowns also includes a need to examine how rapid weight loss may impact ovulation rates and spontaneous conception, as well as miscarriage rates, birth weight, and metabolic health of the child.
More detailed rebound weight gain data is coming next year, with additional analysis expected as well on birth weight and pregnancy outcomes, said Jacqueline Maya, MD, first author of the research abstract presented at this year’s American Diabetes Association conference that examined gestational weight gain among people with preexisting type 2 diabetes who were exposed to GLP-1s during pregnancy. The study included 47 exposed pregnancies (based on prescription records and electronic chart information) and compared gestational weight gain to 141 unexposed matched pregnancies. Among the exposed group, 62% exceeded recommended weight gain, compared with 41% in the unexposed group. On average, gestational weight gain in exposed pregnancies exceeded that among matched unexposed pregnancies by about 6 pounds.
The team is now working with an additional data set to examine exposed pregnancies among people with obesity, said Maya, an instructor of pediatrics at Mass General Hospital and Harvard School of Medicine. She is particularly interested in examining weight trajectories during pregnancy to see how they may affect fetal outcomes. Her team’s current project also will likely include analysis to examine other variables like postpartum weight gain and adiposity characteristics of the baby.
Maya said the team hopes to have more to report at the American Diabetes Association conference in June next year.