Doctors are advising women taking Mounjaro to take extra contraceptive precautions
For couples hoping to have a baby, getting pregnant can be a long and uncertain journey. Some spend years trying to conceive or undergo repeated rounds of IVF before achieving a pregnancy.
Against that backdrop, reports of women becoming pregnant while taking weight-loss medicines have attracted attention. Some have welcomed pregnancies they thought might be difficult to achieve; others have discovered they are pregnant despite using contraception.
Their experiences have prompted questions about whether changes in weight and metabolic health can affect fertility, as well as how women are advised about contraception before starting treatment.
Unexpected pregnancies
Rhiannon Picton-James recently described in The Times becoming pregnant after several years of trying for a second child. She had been taking Mounjaro, while her husband had begun using Ozempic. Last year, the Daily Mail reported the case of Natasha Major, who discovered she was pregnant after starting Mounjaro while taking the contraceptive pill.
Dr Ippokratis Sarris, Director of King’s Fertility and Consultant in Gynaecology and Reproductive Medicine, describes GLP-1 medicines in The Times as “a hot topic right now in fertility”.
Weight loss and improved metabolic health may help restore ovulation in some women whose periods have been irregular, increasing the possibility of pregnancy. Researchers are still investigating the relationship, and the medicines are not established fertility treatments.
Mounjaro contains tirzepatide, which slows the emptying of the stomach and can affect the absorption of medicines taken by mouth. The UK Medicines and Healthcare products Regulatory Agency (MHRA) advises women taking Mounjaro who use the pill to add a barrier method for four weeks after starting treatment and for four weeks after each dose increase.
The MHRA also says Mounjaro should not be taken during pregnancy or just before trying to conceive, because there is not enough safety data. It recommends stopping it at least one month before a planned pregnancy.
Fertility and pregnancy
There is also the possibility that weight-loss medicines could affect male reproductive health. Researchers from University Hospitals Coventry and Warwickshire and Warwick Medical School reviewed five clinical trials and found early indications of improvements in some reproductive measures among men with obesity. However, they do not yet know whether treatment increases the chance of conceiving or having a baby, or how much of any change is related to weight loss.
For women, finding out that a pregnancy has begun while taking a weight-loss medicine can be worrying. A recent review led by City St George’s, University of London, offers some reassurance for those who took a GLP-1 medicine around conception before realising they were pregnant. The review included 8,325 women who had been exposed and found no clearly detectable increase in the adverse outcomes studied.
Although there is still more research needed in this area, the findings may ease some anxiety for people who did not expect to be expecting.
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