Claims that “skinny jabs” are fueling an unexpected baby boom have led experts to warn women to combine their use with effective contraception.
Drugs such as Wego and Ozempic, both of which contain semaglutide, have become very 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, which triggers increased insulin production, slowing the rate at which food is digested in the stomach and reducing appetite.
But as their use has boomed, there have also been reports of women becoming pregnant while taking the drugs – known as GLP-1 receptor agonists.
The “I got pregnant on Ozempic” Facebook group has more than 750 members, while threads on the social network Reddit are full of anecdotes about such experiences.
While studies confirming the link are lacking, experts say the association is likely.
“Obese women often have irregular or no periods because they are not ovulating. Once they lose weight, ovulation becomes more regular and so their fertility improves,” said Dr Karin Hammarberg from Monash University in Australia.
Research is underway to investigate whether semaglutide could help increase ovulation in women with obesity and polycystic ovary syndrome (PCOS), a condition that can cause irregular periods, weight gain and infertility, among other things.
However, concerns have been raised about the safety of pregnant women using GLP-1 receptor agonists.
A spokesman for Novo Nordisk, which makes Ozempic and Wegovy, said: “Pregnancy or intention to become pregnant were exclusion criteria in our studies of semaglutide in both obesity and type 2 diabetes. Therefore, there are limited data from clinical trials with the use of semaglutide in pregnant women.
While evidence in humans is lacking, animal studies suggest that semaglutide may cause fetal abnormalities.
According to Novo Nordisk, when semaglutide was administered to pregnant rats, the unborn offspring showed structural abnormalities as well as growth changes.
The preclinical safety information for the Wegos adds: “In developmental toxicity studies in rabbits, a cynomolgus in monkeys, increased pregnancy loss and a slightly increased incidence of fetal abnormalities were observed at clinically relevant exposures.”
While the company is now conducting trials to determine whether such drugs are safe for pregnant women, it currently recommends that semaglutide not be used during pregnancy because it is not known whether it can affect an unborn baby.
“Therefore, the use of contraception is recommended while taking this medicine,” Wego’s patient information leaflet states. “If you wish to become pregnant, you should stop using this medicine at least two months in advance. If you become pregnant, are pregnant, think you may be pregnant, or are planning to become pregnant while taking this medicine, talk to your doctor immediately as treatment will need to be stopped.
However, some women have reported becoming pregnant while taking GLP-1 receptor agonists despite using hormonal birth control, leading to speculation that the drugs may interfere with these methods of birth control.
Professor Sir Stephen O’Rahilly, co-director of the Wellcome-MRC Institute of Metabolic Science, said the question of whether GLP-1 agonist drugs could interfere with the effectiveness of oral contraceptives was still largely unanswered.
“People treated with these drugs can develop gastrointestinal side effects, including diarrhoea, so it is not unlikely that some women may find that their oral contraceptive pill is not, at least occasionally, as reliably absorbed as it used to be,” he said.
“A pragmatic response to this situation may 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 may consider themselves to be at higher risk of pregnancy and use other methods such as barrier contraception until their weight stabilizes, after which it seems likely that contraceptive effectiveness will return to normal.’
Hammarberg agreed. “The stories of women on semaglutide who got pregnant while on the pill are anecdotal stories and we need to be aware that this happens to women who are not on semaglutide. Some speculate that semaglutide may alter the absorption of the pill, but as far as I know, there is no evidence that this is the case,” she said.
“To be doubly sure that an unplanned pregnancy does not occur, it may be wise for women taking Ozempic and similar drugs to use condoms, and of course an IUD would also be a very safe option.”