Women using weight-loss jabs are being advised to stop if they are trying for a baby, have fallen pregnant or are breastfeeding.

Drug safety experts in the UK say it’s not known whether taking the medicines, such as Wegovy and Mounjaro, could harm an unborn baby.

The advice already appears in patient information leaflets that come with the medicines.

But there are concerns that the growing popularity of ‘skinny jabs’ means many women aren’t using the drugs safely or getting the right advice.

Natasha Major, 26, started using Mounjaro to lose weight before planning to try for her third baby in a few years’ time, but was shocked six weeks later to find she was pregnant. She was taking the contraceptive pill at the time.

“I have polycystic ovaries as well, so I can’t get pregnant easily or quickly. So it was an even bigger shock that I had, which didn’t make any sense to me,” she says.

She then worried she could be harming the baby or it wouldn’t develop properly, so she rang her GP for advice, who told her to stop taking it.

“We’re over the initial shock now and really happy, just wasn’t expected,” she says.

“The last injection I took, I found out about the pregnancy three hours later and haven’t taken it since then.

“I’ve had an early scan to make sure the pregnancy was viable and okay – baby had a little heartbeat and everything looks good,” Natasha says.

As a precaution, the Medicines and Healthcare products Regulatory Agency (MHRA) says women should use contraception while taking GLP-1 medicines and for a certain period afterwards before trying to become pregnant – two months for Wegovy and Ozempic, and one month for Mounjaro.

It also advises that those using Mounjaro and taking an oral contraceptive should also use a condom for four weeks after starting the drug, or switch to another method such as the coil or implant.

Weight-loss jabs may make the contraceptive pill less likely to work in those who are overweight or obese, the MHRA says.

Women should be told this information when they starting taking the jabs, but there are fears the message is not getting through.

Natasha bought Mounjaro online and says she “can’t remember reading anything about contraception on there”.

The MHRA has produced new guidance on weight-loss jabs for people taking them.

It’s acted now because of a very small number of reports of unintended pregnancies and complications in pregnancy made to its Yellow Card scheme, where the public can report suspected side-effects of medicines.

Dr Alison Cave, chief safety officer at the MHRA, said there was evidence from animal studies “that these medicines may harm the unborn baby”.

“But we don’t know whether we have the same effects in humans, so much more data is needed to determine that.”

Women of child-bearing age are usually not included in clinical trials, which is why there is a lack of safety information for them.

“If you are taking this medicine and you are pregnant, you should talk to your doctor about stopping the medicine as soon as possible,” she said.

Sukhi Basra, vice-chairwoman of the National Pharmacy Association, said women should visit their pharmacist for advice if they are confused about when to stop using the drugs.

When it comes to accessing contraception, BPAS, the British Pregnancy Advisory Service, says women in the UK “face significant challenges” when trying to access their method of choice.

A lack of appointments, long waiting lists and high costs are just some of the barriers they face, BPAS said, as it called for a better plan for providing the choice women need.