Catera Bentley stared at the positive pregnancy test and couldn’t believe her eyes. She took a second test, then a third. There was no question — she was pregnant.
She called her husband at work and told him there was a giant spider in the house he had to come get rid of. He rushed home and, when he arrived, Bentley revealed the news.
They both burst into tears.
The couple, who live in Steele, Alabama in the US, had been trying to have a child for more than two years, but Bentley’s doctor had told her she may be unable to conceive because of her history of polycystic ovary syndrome, known as PCOS.
The news had left her feeling without a purpose.
“That’s all I wanted to be … a mum and a wife,” Bentley, 25, said.
“I was depressed, severely depressed for that whole time.”
Five months earlier, in October 2022, Bentley had started taking Mounjaro for weight loss.
Over the first few months, she said, she lost about 18kg. Her menstrual cycles, which had been irregular because of PCOS, became normal. And she even felt happier.
“It just made me feel like a whole new person,” she said. “I was in a better mood every single day.”
Bentley had hoped losing weight might help her get pregnant, and she’d heard about others having success with weight loss while taking the shot.
But when she did become pregnant — sooner than she expected — she worried about the effects it might have on her baby.
‘Ozempic babies’
Bentley is far from alone. Numerous women have shared stories of “Ozempic babies” on social media.
But the joy some experience in discovering pregnancies may come with anxiety about the unknowns, as these medicines have not been studied in people who are pregnant.
“We don’t know the effect of early exposure … on the foetus,” said Dr Jody Dushay, a physician focused on endocrinology and metabolism at Beth Israel Deaconess Medical Centre and an assistant professor at Harvard Medical School.
Dushay said she recommends women stop taking these drugs two months before trying to get pregnant, as directed in the prescribing information.
Ozempic and Mounjaro are part of a class of drugs called GLP-1 receptor agonists, which act by mimicking hormones in the gut involved in insulin regulation and appetite.
Both are approved to treat type 2 diabetes, and each has a twin medicine approved for weight loss.
Ozempic uses the active ingredient semaglutide, with Wegovy the version approved for weight loss, while Mounjaro uses tirzepatide, which also targets a second hormone called GIP, and Zepbound is its brand name for weight loss.
The medicines have been shown to help people lose 15 per cent to 20 per cent of their body weight, on average, in clinical trials.
And because of the way GLP-1 drugs work, experts say, there are reasons they may lead to more pregnancies — as well as cause for caution about their use in early pregnancy.
An effect on birth control
For one, weight loss can generally be associated with increased fertility by restoring normal ovulation in people who have PCOS or other causes of abnormal cycles, said Dr Daniel Drucker, a professor and researcher at the University of Toronto’s Mount Sinai Hospital and a pioneer of research into GLP-1.
“If you start on these medicines and then you lose 5, 10, 15 per cent of your body weight, very often, you will have an improvement in ovulation,” Drucker said.
One scenario that is “quite conceivable” is someone who has obesity and infrequent menstrual periods starts one of these medicines, loses weight but finds they are still not having regular periods — “only now it might be because you’re pregnant”, he said.
Mounjaro and Zepbound also warn in their prescribing information they may render birth control pills less effective.
Drucker said this may be because the drugs work in part by slowing the rate at which food moves through the stomach. This can make people feel full for longer but also could interfere with absorption of other medicines, including birth control pills.
Mounjaro and Zepbound warn about this explicitly on their labels, but Ozempic and Wegovy only warn more broadly about absorption of any drugs taken by mouth.
Safety in pregnancy
Even as GLP-1 medicines may increase fertility, little is known about their safety during pregnancy. The drugs’ makers, Novo Nordisk and Eli Lilly, excluded people who were pregnant or planned to become pregnant from their clinical trials — a common practice when testing new medicines.
But that doesn’t mean there’s no information available.
“The more these meds are used, the more women will get pregnant while taking them and we will in that way accumulate data on risk of early pregnancy exposure,” Dushay explained.
In other words: “We basically gather data from ‘accidents’ as we do for most drugs.”
The few studies available about babies whose mothers took GLP-1s early in pregnancy haven’t turned up major causes for concern, although researchers note that more study is needed — and it’s underway.
Novo Nordisk has a registry collecting data about the safety of Wegovy during pregnancy, which a company spokesperson says will be disclosed at the end of the study — believed to be in 2027.
An Eli Lilly spokesperson said the company also plans to open a pregnancy registry for Zepbound, which was approved at the end of last year.
Studies in animals, though, have suggested some cause for caution, Drucker said.
“If animals get high doses of these drugs, very often, the babies … are small and, sometimes, they have some malformations,” he noted.
That’s probably because the drugs also work by reducing appetite.
“If you restrict energy intake in a pregnant animal, then the baby is not going to get enough nutrients and won’t be able to grow properly,” Drucker said.
He also pointed to a study in animals suggesting GLP-1 drugs may reduce the number of proteins often found in the placenta that are responsible for transferring nutrients from the mother to the foetus.
Already in use for PCOS
Those concerns complicate research on the medicines for infertility, but some work is ongoing on one of the most common causes: PCOS.
The condition affects as many as 12 per cent of women of reproductive age in the United States, according to the US Centers for Disease Control and Prevention.
The exact cause of PCOS is unknown but it is associated with excess weight, which is thought to contribute to the body’s production of too much insulin.
That, in turn, results in hormonal imbalances — specifically, higher levels of hormones such as testosterone, which can stop ovulation and cause irregular periods, acne and excess facial hair, according to the CDC.
Although there’s no cure, weight loss alone can lead to significant improvement of symptoms and resumption of regular ovulation and menstruation, said Dr Anuja Dokras, director of the PCOS clinic at the University of Pennsylvania.
Lifestyle changes are the first-line treatment for PCOS but, if those interventions aren’t successful, doctors may prescribe Ozempic or other GLP-1 agonist medications, Dokras said.
The 2023 international PCOS guidelines list GLP-1 agonists among the medications for “management of higher weight in adults with PCOS”.
GLP-1 agonists improve insulin resistance and lead to weight loss, so it makes sense that they also improve PCOS symptoms, added Dr Melanie Cree, director of the multidisciplinary PCOS Clinic at Children’s Hospital Colorado.
“It is completely being used now with no evidence because the (obstetrics) field knows that if you have 5 per cent weight loss in these individuals with PCOS, you will improve fertility,” she said.
Cree is now running a clinical trial, funded by the National Institutes of Health, that will look specifically at fertility outcomes for young women with PCOS who take semaglutide.
But Cree pointed to another question about the medicines during pregnancy: the potential for quick weight regain that can happen when patients stop them suddenly.
“If that’s happening in the setting of pregnancy, when you’re gaining all this weight, what happens?” she asked.
“What does that mean? And we just don’t know.”
A ‘Catch-22’
The drugs’ makers are also following the “Ozempic babies” phenomenon. Eli Lilly’s chief of research, Dr Daniel Skovronsky, says the company has heard these kinds of stories from patients.
“One question we’re asking is: is it possible that, as we reduce fat, we improve fertility, decrease PCOS and other barriers to fertility?” Skovronsky said.
“It’s kind of like heart failure or sleep apnoea,” he said, referring to conditions for which GLP-1 drugs have recently shown positive results.
“Just another potential benefit of weight loss from this class of medications that we haven’t tested yet.”
He also underlined how tricky it is to run studies around fertility of medicines whose safety in pregnancy is unknown. Cree referred to a requirement for birth control in studies of GLP-1 drugs as a “Catch-22” for fertility indications.
“Right now, unfortunately, it’s really hard to study the effects of these drugs on fertility, because that implies exposing women to a drug with a high risk that they’ll have a pregnancy during exposure to the drug and the risks to the baby haven’t been fully analysed yet,” Skovronsky said.
Bentley, who got pregnant while taking Mounjaro, said she stopped taking the medicine as soon as she found out she was pregnant. But she said she continued to worry about the effect of the drug on her baby.
“I worried up until the day I had her,” she said.
Her daughter, Ivy, was born healthy on her due date, weighing 3.4kg. Bentley started taking Mounjaro again six weeks after Ivy was born.