The rising popularity of weight loss medications like Wegovy and Zepbound has sparked new conversations — not just about side effects, but about their potential impact on fertility.

While these drugs are primarily prescribed for weight loss and diabetes management, they have also raised questions about unexpected reproductive effects.

Among them: whether medications may increase fertility in some people and whether they could potentially interfere with birth control.

Much remains unknown about the long-term effects of these medications, as many are relatively new, and long-term studies on their effects — particularly on reproductive health — are still in early stages.

Samantha Schon, M.D., an assistant professor in the University of Michigan Department of Obstetrics and Gynecology studies the role of obesity in fertility outcomes.

Schon, who directs the Michigan Interdisciplinary Clinic for Obesity and Reproduction, discusses what is known – and still unknown – about the connection between weight loss medications, obesity, and fertility.

Connection between weight loss drugs and fertility

Obesity has a well-established and often complex impact on female fertility, Schon explains.

It can cause anovulation or irregular periods in which the ovaries fail to release an egg regularly. It can contribute to polycystic ovary syndrome, a hormonal disorder that can be exacerbated by weight gain.

Clinically, women with obesity typically need higher doses of fertility medications, experience longer times to conception and have a higher risk of miscarriage, Schon says.

What’s less clear, however, is exactly how weight loss – particularly from weight loss medications – modifies these fertility challenges.

“With these so-called ‘Ozempic babies,’ what we’re seeing most often is that women who weren’t ovulating regularly begin to ovulate again after losing weight, and then become pregnant,” said Schon.

“So it’s likely not the medications themselves directly causing pregnancy, but rather the weight loss leading to the return of regular cycles.”

Still, Schon notes that newer weight loss medications haven’t been tested long enough to know if – or how – they may influence pregnancy rates independently.

These newer medications, Schon says, do lead to higher percentages of weight loss, averaging between 15 to 20% or higher, compared to previous ones that achieve closer to five percent weight loss.

That level of weight reduction could have more noticeable effects on fertility, making it an important area for future research as more data becomes available, she says.

Weight loss as part of the fertility treatment process

While weight loss can play an important role in fertility treatment, maternal age remains the strongest predictor of treatment success, Schon says.

“As women become reproductively older, the benefits of weight loss on fertility outcomes tend to diminish,” Schon says.

“We see a more significant impact in younger women, where weight loss can meaningfully improve ovulation and pregnancy chances.”

Part of Schon’s work involves guiding patients through the fertility journey – helping them weigh the potential benefits of weight loss against other critical factors, such as age and treatment timelines.

“We try to balance the chances that weight loss will help fertility treatment with our ultimate goal of setting women up for the healthiest pregnancies possible,” said Schon.

“A big part of that is evaluating whether there’s enough time to focus on optimizing health before trying to conceive. We personalize treatment based on factors like the patient’s age, health, and personal goals.”

In many cases, there is time to pursue weight loss, which can improve outcomes. But for other individuals, delaying treatment for significant weight loss may reduce the chances of conceiving with their own eggs, Schon says.

GLP-1s and birth control

In addition to fertility concerns, questions have also emerged around whether GLP-1 medications might interfere with the effectiveness of hormonal birth control.

Health officials in the United Kingdom recently issued guidance warning people that weight loss medications might be interfering with certain birth control methods.

Their report suggests some women on weight loss medications are getting pregnant while simultaneously using birth control. 

Schon says some pharmacologic data shows tirzepatides, also known as Mounjaro or Zepbound, may decrease the peak levels of contraceptive hormones in the bloodstream.

Because of this, manufacturers recommend using a backup form of contraception during the first four weeks of a new tirzepatide regimen.

Currently, the concern applies primarily to hormonal birth control methods, such as birth control pills.

“Pharmacological data suggests there might be some interaction between these drugs, but it is unclear if this translates into reduced clinical effectiveness,” said Schon.

“So far, we haven’t seen a significant number of reported cases in the literature where women are becoming pregnant while using both weight loss medications and hormonal birth control. This is certainly an area where more research is needed.”

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