Claims that “skinny jabs” are fuelling an unexpected baby boom have led experts to warn women to pair their use with effective contraception.
Medications such as Wegovy and Ozempic, both of which contain semaglutide, have become hugely popular, not least because they can help people lose more than 10% of their body weight.
The drugs work by mimicking a hormone in the body called GLP-1 that triggers an increase in the production of insulin, slows the rate at which food is digested in the stomach, and reduces appetite.
But as their use has boomed, so too have reports of women falling pregnant while using such medications – known as GLP-1 receptor agonists.
The Facebook group “I got pregnant on Ozempic” has more than 750 members, while threads on the social network site Reddit are replete with anecdotes of such experiences.
While studies confirming a link are lacking, experts say an association is plausible.
“Women with obesity often have irregular or no periods because they don’t ovulate. Once they lose some weight, ovulation becomes more regular and this is how their fertility improves,” said Dr Karin Hammarberg of Monash University in Australia.
Research is under way to explore whether semaglutide could help boost ovulation in women with obesity and polycystic ovary syndrome (PCOS) – a condition which can cause irregular periods, weight gain, and infertility among other symptoms.
However, concerns have been raised over the safety of pregnant women using GLP-1 receptor agonists.
A spokesperson for Novo Nordisk, the company that makes Ozempic and Wegovy, said: “Pregnancy or intention to become pregnant were exclusion criteria in our trials with semaglutide in both obesity and type 2 diabetes. Therefore, there are limited clinical trial data with semaglutide use in pregnant women.”
While evidence in humans is lacking, animal studies have suggested semaglutide can cause foetal abnormalities.
According to Novo Nordisk, when semaglutide was given to pregnant rats, the unborn offspring showed both structural abnormalities and alterations to growth.
The preclinical safety information for Wegovy adds: “In developmental toxicity studies in rabbits and cynomolgus monkeys, increased pregnancy loss and slightly increased incidence of foetal abnormalities were observed at clinically relevant exposures.”
While the company is now carrying out trials to explore whether such drugs are safe for pregnant women, at present it advises that semaglutide should not be used during pregnancy as it is not known if it may affect an unborn child.
“Therefore, it is recommended to use contraception while using this medicine,” the patient information leaflet for Wegovy states. “If you wish to become pregnant, you should stop using this medicine at least two months in advance. If you become or are pregnant, think you may be pregnant or are planning to have a baby when using this medicine, talk to your doctor straight away, as your treatment will need to be stopped.”
But some women have reported becoming pregnant when using GLP-1 receptor agonists despite using hormonal contraception, leading to speculation the drugs might interfere with such methods of birth control.
Prof Sir Stephen O’Rahilly, co-director, of the Wellcome-MRC Institute of Metabolic Science, said the question of whether GLP-1 receptor agonist drugs can interfere with the efficacy of oral contraceptives is, so far, largely unanswered.
“People treated with these drugs can develop gastrointestinal side-effects including diarrhoea, so it is not implausible that some women may find that their oral contraceptive pill is, at least intermittently, not as reliably absorbed as it was previously,” he said.
“A pragmatic response to this situation might be to suggest that for women who are on the pill and very keen to avoid pregnancy, that while they are experiencing active weight loss on GLP-1 [receptor agonists], they might consider themselves to be at higher risk of pregnancy and use additional methods, such as barrier contraception, until their weight stabilises, after which it seems likely that contraceptive efficacy would return towards normal.”
Hammarberg agreed. “Stories of women on semaglutide getting pregnant while on the pill are anecdotal accounts and we have to remember that this also happens among women who are not taking semaglutide. Some speculate that semaglutide might change the absorption of the pill but as far as I know there is no evidence that that is the case,” she said.
“To be doubly sure that unplanned pregnancy doesn’t happen, it may be wise for women who are on Ozempic and similar drugs to use condoms and of course an IUD would also be a very safe option.”