Source: United Kingdom – Executive Government & Departments
Scientists comment on the MHRA advice on contraceptives for women taking weight loss drugs.
Dr Bassel Wattar, Consultant Obstetrician and Gynaecologist, Epsom and St Helier University Hospitals, said:
“GLP-1 agonist drugs are a great new addition to help selected patients with weight issues achieve a better health status. The challenge is to regulate their use and couple it with adequate medical monitoring to minimise the risks of adverse events. To date, women planning for pregnancy or those pregnant were largely excluded from clinical trials that evaluated the efficacy and safety of these medications. There is some data from animal studies to suggesting there is a risk of malformation to the fetus, in animals falling pregnant while taking GLP-1 agonists, but data remains limited in humans. The warning from the MHRA is timely to govern and guide on the safe use of these medications, especially for women struggling to lose weight and hoping to get pregnant.
“It is important to recommend effective contraception while taking these injections such as the implant or the intrauterine coil, which offer more robust contraception in these cases versus the oral combined contraceptive pill. More importantly, achieving significant weight loss can sometimes help some women (for example those with polycystic ovary syndrome) to restore natural ovulation, and therefore, boost their chances of falling pregnant spontaneously without needing invasive fertility treatment like IVF. This however, should be planned under the care of a specialist fertility doctor to ensure a pregnancy can be planned safely after a washout period off these drugs.”
Dr Channa Jayasena, Reader in Reproductive Endocrinology at Imperial College London and Consultant in Reproductive Endocrinology and Andrology at Imperial College Healthcare NHS Trust, Imperial College London, said:
“GLP-1 drugs copy the natural hormones made in the gut which make you feel full. This makes them powerful treatments to help women lose weight. Obesity reduces fertility in women. So, women with obesity taking GLP-1 drugs are more likely to get pregnant than before they lost weight. In addition, we think that the absorption of oral contraceptive pills may be reduced with GLP-1 drugs which slow down emptying of the stomach, though more research is needed to confirm this. The guidance produced by the MHRA is sensible, since it highlights that women could accidentally get pregnant when taking GLP-1 drugs. We don’t know how harmful GLP-1 drugs are during pregnancy; however, we know that other forms of weight loss like weight loss surgery can increase chances of a miscarriage. So, women are advised to do all they can to prevent pregnancy while taking GLP-1 drugs.”
Prof Rebecca Reynolds, Professor of Metabolic Medicine, University of Edinburgh, said:
“It is very important to raise awareness about this MHRA advice among women and clinicians around potential issues with GLP-1 drugs affecting the effectiveness of oral contraceptives in those who are overweight. Many people are buying weight loss drugs online and so may not receive this important advice about contraception.
“There is hardly any available data from human studies to be able to advise if these weight loss drugs are safe in pregnancy. The data from animal studies suggests the potential for harm with low birthweight and skeletal abnormalities, though more evidence is needed to assess if there are risks of taking these drugs in humans.”
The MHRA guidance, ‘GLP-1 medicines for weight loss and diabetes: patient factsheet’, was published by the MHRA and is embargoed untiled 00:01 UK time on Thursday 5 June 2025.
Declared interests
Prof Rebecca Reynolds: I have no conflicts of interest to declare
Dr Channa Jayasena: None.
Dr Bassel Wattar: No conflict of interest to disclose