Taking Weight Loss Medication During Pregnancy: Is It Safe?

Pregnancy affects every aspect of a person’s life. Pregnant individuals may think more carefully about what they put into their bodies than ever before. Medications, an important and common element of modern healthcare, can take on new significance during this crucial time.

According to the Centers for Disease Control and Prevention, 9 out of 10 women report taking some type of medication during pregnancy. However, pregnant individuals are rarely included in clinical trials since new medications might pose unforeseen risks to fetuses. This means we may not always know the risks of taking certain medications, including weight loss medications. Notably, Ozempic (semaglutide) has not been studied in pregnant people, and a phenomenon of “Ozempic babies” has arisen. Different ideas are circulating about why these unexpected pregnancies occur and what we still need to learn about the medication’s potential risks to pregnancy.

When treating pregnant patients with obesity, it is important to weigh the risks of obesity itself against any potential risks and benefits of prescribing a weight loss medication.

Impact of Obesity on Pregnancy and Fertility

Obesity affects every stage of pregnancy, from preconception to labor and delivery, and can have implications for the long-term health of the parent and child. It increases risks for induction of labor, cesarean delivery, preterm delivery, anesthesia complications, postpartum hemorrhage, wound complications, DVT/PE, and postpartum depression. Even modest weight reduction can significantly reduce pregnancy risks.

Weight Loss Medications and Fertility

According to a literature review published in 2018, women with obesity have a risk of infertility that is three times greater than their counterparts without obesity. Polycystic ovary syndrome (PCOS) is a common culprit. It occurs when the body doesn’t make enough of the hormones needed to spur ovulation. Obesity and insulin resistance are risk factors, along with genetics. Treating obesity and/or diabetes, therefore, can reduce the effects of PCOS.

Weight loss medications can lead to increased fertility, perhaps by restoring a regular menstrual cycle. It has been speculated that someone with an already irregular cycle might not notice a missed period right away, which is why some of these “Ozempic babies” are such a surprise. However, irregular periods are not the only piece of the puzzle. According to the Mayo Clinic, “Even in women who regularly ovulate, the higher the BMI, the longer it may take to become pregnant.”

Research is now exploring whether the class of drugs that includes GLP-1 and GLP-1/GIP receptor agonists (which we will shorten here to “GLP-1s”) could be used purposefully to overcome infertility. In the meantime, the FDA has asked the manufacturers of GLP-1s currently on the market to create registries for collecting data on people who get pregnant while using them.

GLP-1s and Birth Control

For patients actively trying to avoid pregnancy, newer weight-loss medications may not be the best choice. Tirzepatide, the medication marketed as Mounjaro (for diabetes) and Zepbound (for obesity) includes a warning that it may render birth control pills less effective. Because these medications slow down stomach emptying, they can interfere with how the body absorbs medications. Patients in this situation should be advised to adopt a non-hormonal form of birth control.

Are Weight Loss Medications Safe During Pregnancy?

While weight loss drugs seem like a boon to fertility, all of those currently on the market—not just GLP-1s—are contraindicated for pregnancy. For example, phentermine (Adipex or Suprenza) has been associated with fetal stroke. Prescription medications are not the only cause for concern. Studies have also linked herbal supplements used for weight loss with miscarriage. Likewise, the hydrogel device Plenity is contraindicated.

Aside from the effects of the drugs themselves, there is the question of whether it’s safe to intentionally lose weight (by any means) during pregnancy. Treating obesity through diet and exercise is linked with better outcomes, at least according to a study published in 2012 in the British Medical Journal. These interventions significantly reduce the risk of preeclampsia (33%) and gestational diabetes (61%). Introducing medication into the picture is another thing entirely.

Research is ongoing, but one study of patients with T2D, published in early 2024, indicated that GLP-1s did not increase the risk of major congenital malformations compared to those taking insulin. Other studies have so far only taken place in animal models. The OMA will strive to keep obesity medicine practitioners up to date as research grows.

Should Pregnant Women Stop Taking Weight Loss Medications?

A big question clinicians will likely hear is whether someone needs to stop taking Ozempic, Wegovy, or Zepbound once they get pregnant. Guidelines for these drugs indicate that a person should stop them two months before getting pregnant. However, what about those surprise situations?

When prescribing a weight loss medication, it’s important to walk the patient through any future possibility of pregnancy, along with side effects. Patients are advised to stop taking GLP-1s immediately upon learning that they’re pregnant. The sudden stop can lead to intense withdrawal symptoms, including rapid regain of the weight. As the provider, it is important to focus on lifestyle interventions to make their transition off of medication as smooth as possible.

Weight Loss Medications and Breastfeeding

Parents with overweight or obesity are less likely to breastfeed for a variety of reasons. For one, obesity is a factor in delayed lactogenesis. However, there are many benefits to breastfeeding, and patients of all weights may look to their doctors for support in doing so.

Just as weight medications are contraindicated for pregnancy, they are generally contraindicated for breastfeeding. In the case of GLP-1s, this is largely due to a lack of knowledge about their effects. It is not known whether these medications are excreted in breast milk or how they would affect an infant.

Rapid weight loss can negatively impact milk production in and of itself. Therefore, restarting any weight loss medication while breastfeeding has the potential for negative effects. As with pregnancy, the ideal route may be to help the patient focus on diet and exercise, at least until more research has been done on weight loss medications and postpartum health.

Though it focuses on a man and is not related to pregnancy, this case study looks at one patient’s experience restarting semaglutide after a lapse. It suggests that if a patient restarts these medications after a lapse, they should return to a starter dose and titrate back to their original dose. A single case, of course, is not enough to guide clinical practice.

Alternative Weight Loss Methods During Pregnancy

Is weight loss medication during pregnancy safe? The short answer is that when it comes to newer medications, we don’t know yet. The safest approach is to encourage patients to achieve and maintain a healthy BMI before they get pregnant. However, as discussed, pregnancies are not always planned.

An obesity medicine specialist is a valuable pregnancy care team member. Make sure patients understand the guidelines for healthy weight gain during pregnancy. Reinforce that a certain amount of weight gain is necessary and expected. Explain to them the risks of excessive weight gain, such as complications during birth and risks to their own and the infant’s health. Along the way, they should not only have their weight monitored but also be assessed for sleep apnea, glucose intolerance, and cardiovascular disease.

For pregnant patients with overweight or obesity, focus on three of the four pillars of obesity treatment: nutrition therapy, physical activity, and behavior modification. (The fourth is medical interventions.) When providers treat obesity as the disease that it is, they can help alleviate some of the emotional and societal pressure that a pregnant person may already be experiencing.