The Medicines and Healthcare products Regulatory Agency (MHRA) has issued an urgent warning that weight loss injections such as Ozempic, Wegovy, and Mounjaro may make contraception less effective and could harm unborn babies. Women using these drugs are advised to use birth control, and those on Mounjaro should 'double-up' on contraception if taking the Pill.
Mounjaro, known as the 'King-Kong' of weight loss jabs, may reduce the effectiveness of oral contraceptives in overweight individuals, the MHRA stated. Safe sex is particularly important for the four weeks after starting Mounjaro and after any dose increase. Women who become pregnant while using these medications must stop taking them immediately due to insufficient safety data on potential harm to the baby.
The regulator has received over 40 reports of pregnancy-related issues among women on these drugs, including 26 related to Mounjaro, one of which was an unintended pregnancy. Eight reports involved semaglutide, the active ingredient in Ozempic and Wegovy. Reported problems include birth defects, miscarriages, and unplanned pregnancies.
Experts believe that GLP-1 drugs like Mounjaro slow stomach emptying, which may reduce absorption of oral contraceptives. Dr Channa Jayasena of Imperial College London noted that more research is needed but advised women to prevent pregnancy while taking these drugs. Professor Rebecca Reynolds of the University of Edinburgh added that animal studies suggest potential harm, including low birthweight and skeletal abnormalities.
The MHRA also warned against buying these medicines from unregulated sellers such as beauty salons or via social media. Dr Alison Cave, MHRA chief safety officer, emphasised that these are powerful medicines not intended for cosmetic weight loss. Patients should continue contraception for up to two months after stopping the drugs before attempting pregnancy.
