Researchers Urge Greater Public Awareness of Risks Involving Weight-Loss Drugs and Pregnancy

The nation’s leading group of obstetricians issued long-awaited guidance on October 23 for weight-loss drugs and pregnancy. It tells doctors to warn patients that the safety data are thin and to recommend stopping GLP-1 drugs one to two months before trying to conceive.The American College of Obstetricians and Gynecologists estimates that as many as one in 300 women is now exposed to the drugs before pregnancy. Its advisory recommends against using them at any point while pregnant.What the advisory cannot fix by itself is a problem that starts earlier. Millions of American women are injecting GLP-1 drugs every week without knowing the shot can undermine the pill they count on to prevent pregnancy.Prescriptions have climbed across nearly every age group. Awareness of what the drugs can do to birth control, and to the pregnancies that follow, has not kept pace.A physician-scientist who studies the drugs’ effects on bone and metabolism says the breakdown is one of communication.“There is a huge gap between providers and patients during pregnancy with regard to GLP-1,” the director of clinical and translational research and a senior scientist at Maine Medical Center’s Research Institute, Dr. Clifford Rosen, tells The New York Sun.The Pill Problem Nobody Warned You AboutThe mechanism is not complicated, but it is consequential. GLP-1 drugs work in part by slowing gastric emptying, the rate at which food and medication move through the digestive system. That delay produces the feeling of fullness women are paying for. It can also compromise a pill that depends on the gut for absorption.The prescribing information for tirzepatide, sold as Mounjaro and Zepbound, advises women on oral contraceptives to switch to a non-oral method or add a barrier method. The precaution covers the four weeks after starting the drug and four weeks after each dose increase. But few women, or their prescribing doctors, seem to have gotten the message.In Australia, researchers at Flinders University tracked more than 18,000 women aged 18 to 49 who were first prescribed GLP-1 drugs between 2011 and 2022. Only 21 percent had told their doctors whether they were using contraception, and 2.2 percent became pregnant within six months of starting treatment. By 2022, fewer than 10 percent of new prescriptions in the group went to women with diabetes, the disease for which the drugs were initially developed.A literature review published in the Journal of the American Pharmacists Association concluded that the tirzepatide interaction creates a particular need for better education for both providers and patients. The doctor who prescribes the GLP-1 and the one who prescribes the contraceptive are often different physicians who may never discuss the interaction.The risk is not uniform across the drug class. Tirzepatide is the outlier: a single 5 mg dose cut overall exposure to an oral contraceptive by about 20 percent. Studies of other GLP-1 drugs, including semaglutide, the active ingredient in Ozempic and Wegovy, have not found a statistically or clinically significant drop.Regulators abroad have moved faster to reach patients. Britain’s Medicines and Healthcare Products Regulatory Agency issued public guidance in June 2025. It advised women on Mounjaro who use the pill to add a non-oral method, especially in the four weeks after starting the drug or raising the dose. Australia’s Therapeutic Goods Administration concluded in late 2025 that reduced effectiveness during that window could not be ruled out and updated product warnings. In the United States, the warnings sit in prescribing information and rarely reach patients.The gap showed up in a case presented at the American College of Obstetricians and Gynecologists’ annual meeting in May. An OB-GYN resident physician at NYU Langone–Long Island, Dr. Casey Moffitt, presented the case of a 39-year-old on weekly semaglutide. The patient became pregnant despite reporting consistent use of a combined oral contraceptive. A chart review turned up no missed pills, no interacting medications and no clear explanation.The case prompted Dr. Moffitt and colleagues to review 10 trials and FDA reviews covering 305 patients. The finding cuts two ways. Overall, GLP-1 and dual GLP-1/GIP drugs were not found likely to meaningfully reduce the pill’s effectiveness, though they can lower and delay absorption of its progestin component while leaving estrogen exposure intact. For semaglutide and liraglutide, the review found the pharmacokinetic data reassuring.OB-GYNs, meanwhile, are seeing patients conceive on these drugs while taking pills they had relied on for years.The irony is that GLP-1 drugs can also boost fertility. By reducing insulin resistance, they can restore regular ovulation in women with polycystic ovary syndrome. The hormonal condition is tied to insulin resistance and obesity, disrupts menstrual cycles and leads many women to believe they cannot conceive.A woman who thought her polycystic ovary syndrome protected her from an unplanned pregnancy, now on a drug that restored her fertility and may have weakened her pill, is precisely the patient most at risk.The Risks Don’t End When You Stop the DrugWomen who discover they are pregnant face instructions with uncomfortable implications. The drugs are contraindicated during pregnancy, so the prescription stops. Stopping, however, carries hazards of its own.A study published in JAMA last November drew on nearly 150,000 singleton pregnancies delivered at Mass General Brigham between 2016 and 2025. It matched 448 pregnancies exposed to GLP-1 drugs before or early in pregnancy against 1,344 that were not.Women who used the drugs and then stopped faced a 34 percent higher risk of preterm delivery. They also faced a 30 percent higher risk of gestational diabetes and a 29 percent higher risk of hypertensive disorders of pregnancy.Dr. Rosen says the findings track with what is already understood about stopping the drugs.“When the GLP-1s are stopped, the risk for other diabetes-related complications, especially during pregnancy, increases — certainly gestational diabetes would get worse,” he says.The driver is largely the rebound. Women who stopped GLP-1 drugs gained about 30 pounds during pregnancy, compared with roughly 23 pounds in the comparison group. That metabolic rebound collides with the demands of gestation. It drives excess weight gain, itself a documented risk factor for preterm delivery, gestational diabetes and hypertensive complications including preeclampsia.The study’s lead author, Dr. Jacqueline Maya, a pediatric endocrinologist at Mass General Brigham for Children, noted that GLP-1 use has increased dramatically. Recommendations still call for stopping the drugs before pregnancy because safety data for unborn babies are limited.The senior author, Dr. Camille Powe, co-director of the Diabetes in Pregnancy Program at Massachusetts General Hospital, said more research is needed to weigh the drugs’ benefits before pregnancy against the risks of stopping them.ACOG’s new advisory takes up that problem directly. It urges doctors to encourage lifestyle changes and monitor patients’ weight after they stop the drugs.There is still no clearly safe path. Continue the drug, and the fetus is exposed to an agent never tested in human pregnancy trials. Stop it, and the mother’s metabolic health can deteriorate in ways that drive complications of their own.What Animal Studies Warn About Fetal ExposureThe drugs are not contraindicated in pregnancy out of bureaucratic caution. In rat, mouse and rabbit studies, GLP-1 drugs caused reduced fetal weight and growth, delayed bone formation and skeletal variants such as wavy ribs, with effects increasing at higher doses.In pregnant rats given semaglutide at the human clinical dose, researchers found increased fetal death and physical abnormalities. These included reduced growth, abnormal heart blood vessels and changes to the cranial bones, vertebrae and ribs. ACOG’s advisory cites the same body of evidence: decreased fetal weight, growth restriction, abnormal bone development, and lower maternal food intake and weight gain.Dr. Rosen says the findings do not surprise him.“It’s not surprising that fetal skeletal abnormalities and restricted growth might follow use of GLP-1s in pregnancy, especially early,” he tells the Sun. “We have shown that in mice, bone is definitely adversely affected by the GLP-1s with reduced bone mass, so linear growth would likely also be affected.”Rodent biology does not translate directly to humans. Human data so far, limited to small observational studies, have not shown a clear signal of birth defects. A June study from the Harvard T.H. Chan School of Public Health found that taking the drugs in the first trimester did not appear to substantially raise the risk of adverse outcomes. The numbers are still too small for firm safety conclusions.GLP-1 receptors are present in fetal tissue, and the drugs’ long half-lives complicate a clean stop. Semaglutide has a half-life of about seven days and tirzepatide about five. Wegovy’s prescribing information says to stop at least two months before a planned pregnancy, a window nearly impossible to hit when the pregnancy is unplanned. ACOG’s advisory includes a table of every GLP-1 drug’s half-life for that reason.Britain’s medicines regulator has said plainly that the drugs must not be taken during pregnancy, while trying to conceive or while breastfeeding. Anyone who becomes pregnant on them should stop as soon as possible.ACOG takes a narrower line on breastfeeding. If a nursing mother uses a GLP-1 drug, doctors should closely monitor the baby’s weight gain, and the drugs should be avoided when nursing preterm infants or newborns.What is missing, researchers say, is a systematic effort to close the gap between that guidance and real life. Women pick up a GLP-1 prescription from one doctor and birth control from another, and neither conversation includes the other.Dr. Rosen calls that coordination failure the central problem.“The most important issue is communications about maintaining energy needs for mother and baby in the face of the GLP-1 anorexic effects, and second, discontinuation of the GLP-1s, which can lead to rebound worsening of diabetes and adverse neonatal outcomes,” he says.

Researchers Urge Greater Public Awareness of Risks Involving Weight-Loss Drugs and Pregnancy

Researchers Urge Greater Public Awareness of Risks Involving Weight-Loss Drugs and Pregnancy

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