Why weight-loss drugs may be creating a perfect storm for unplanned pregnancies

Australia’s medicine watchdog says it can’t rule out that weight-loss injections reduce the effectiveness of oral contraceptives, as hundreds of women fall pregnant while using the injections.

Women are advised to stop using GLP-1s – a type of drug used for type 2 diabetes and weight loss – at least one to two months before trying to conceive, due to concerns about the drugs’ potential effect on a developing fetus.

But the drugs may have created a perfect storm for unintended pregnancies: the weight loss they trigger can improve fertility, while the medication may also reduce the effectiveness of oral contraceptives.

Telephone health services are reporting a steady stream of calls from women who have had an unplanned pregnancy while using the medication, a phenomenon that has given rise to the term “Ozempic babies”.

MotherSafe, which provides a counselling service for NSW women and healthcare providers, has received 130 calls this year about GLP-1 exposure during pregnancy.

“It’s important that people plan pregnancies and are aware that these drugs may improve their chances of falling pregnant,” Mothersafe director Dr Debra Kennedy said.

In Victoria, Monash Health has provided help to at least 12 mothers who fell pregnant while using weight-loss injections over the past year. And a Royal Women’s Hospital spokeswoman said its medicines information service was receiving a growing number of inquiries about semaglutide exposure during early pregnancy. (Ozempic is a brand name for semaglutide).

It’s a trend backed up by new research in the Medical Journal of Australia that found 2 per cent of women of reproductive age taking GLP-1s – or 232 women – fell pregnant within six months of starting the treatment. This increased to 4 per cent of women in their peak reproductive years between the ages of 25 and 34.

Lead author Luke Grzeskowiak, a pharmacist and researcher from Flinders University, said animal studies had linked GLP-1 exposure during pregnancy to reduced fetal growth, slowed bone development and reduced maternal weight gain.

While the only human study to date found no association between GLP-1 exposure and congenital malformations, Grzeskowiak noted that it did not examine other potential adverse outcomes.

“The key is making sure that everything is well managed and ensuring that there’s appropriate time between stopping these medications and decisions around pregnancy, to reduce any potential harms,” he said.

Grzeskowiak is concerned about the low take-up of hormonal contraceptives among women aged 18 to 49 using the medication. Just 21 per cent were prescribed contraception, according to the study, which analysed data from more than 1.6 million women aged 18 to 49 who attended general practices between 2011 and 2022.

“We’re seeing widespread use of these medications among women of childbearing age, but very little evidence that contraception is being considered as part of routine care,” he said.

The Therapeutic Goods Administration recently reviewed whether using GLP-1s reduced the effectiveness of oral contraceptives.

“The assessment concluded that reduced effectiveness of oral contraception during initiation or dose escalations with tirzepatide could not be ruled out,” a federal Department of Health spokesman said. Tirzepatide is the generic name for popular weight loss and type 2 diabetes drug Mounjaro.

The spokesman said the TGA would publish any regulatory actions from its review as soon as they were available. He said the TGA had been informed of six reported cases of exposure to semaglutide while pregnant.

In June, UK health authorities advised women using Mounjaro to also use barrier contraceptives such as condoms amid concerns it may reduce the effectiveness of oral contraceptives.

It’s believed that slowing down the emptying of the stomach, a known effect of GLP-1 drugs, may reduce the absorption of contraceptive pills.

The new Australian study also revealed that in 2022, more than 1 in 100 women began treatment on GLP-1s and more than 90 per cent of this group did not have a diabetes diagnosis.

Nisha Khot, president-elect of the Royal Australian and New Zealand College of Obstetricians and Gynaecologists, said losing a significant amount of weight – a common effect of the drugs – also improved women’s fertility.

“When you lose weight, you are more likely to ovulate, because your hormones are better synchronised,” she explained. “I don’t think women are being told that there is a higher chance of pregnancy when using these agents.”

Khot is treating a growing number of women who have become pregnant while using the medication. She said many were anxious about the potential effect of their treatment on their babies, despite the available research showing no clear risk.

Rodney Whyte, a therapeutic medicines specialist at Monash Health and Monash University, advises women to immediately stop using GLP-1s if they have inadvertently fallen pregnant, but also reassures them.

He said many of these women had been incorrectly advised to terminate their pregnancies – or read information suggesting they should – which had caused them deep concern.

“We would strongly advise against that,” he said.

He points to a study in the British Medical Journal that looked at exposure during early pregnancy and found that the drugs were not associated with a risk of major birth defects when compared with diabetes or being overweight or obese.

“There’s a lot of fear and trepidation relating to medicines in pregnancy that’s often overplayed. The medical conditions that we’re treating often have far more significant impacts on outcomes than the medications themselves.”

He said women exposed to these medications during pregnancy might benefit from counselling and additional ultrasounds to monitor their baby’s growth.

“Many of these women have been infertile and they’re finding that within a short time frame they’re inadvertently able to conceive,” he said. “They are really wanted babies in many of these cases.”

Women using GLP-1s to treat type 2 diabetes are urged to speak to their doctor about switching to other medications to manage the disease during pregnancy.

US pharmaceutical company Eli Lilly, which makes Mounjaro, said its product information warned that it should not be used during pregnancy.

“Women of childbearing potential are advised to use contraception during treatment with tirzepatide and if a patient wishes to become pregnant or becomes pregnant, treatment with tirzepatide should be discontinued,” a spokeswoman said.

“We take any reports regarding patient safety extremely seriously and actively monitor, evaluate, and report safety information for all our medicines.”

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