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Scientists comment on the MHRA advice on contraceptives for women taking weight loss drugs.
Dr Caroline Ovadia, Senior Clinical Lecturer in Obstetrics, University of Edinburgh, said:
“Achieving a healthy, stable weight before pregnancy is likely to be of benefit to both maternal and fetal outcomes, and lifelong health of the child; improvement of diseases for which GLP1 RA are indicated, such as type 2 diabetes and obesity, is likely to significantly reduce important pregnancy outcomes such as miscarriage, stillbirth, neonatal death, and congenital anomaly (based upon data from individuals with pregestational diabetes).
“Human evidence for the risk of GLP1 RA in pregnancy is limited, but existing cohort studies, predominantly from the US, where “weight loss” medication use is particularly common, does not suggest immediate harm.
“Some side effects of GLP1 RA, such as pancreatitis, are independently predisposed in pregnancy, and so theoretical increased risks of harm may occur for individuals continuing GLP1 RA during pregnancy, although clinical evidence has not yet supported this (lack of evidence).
“Anecdotally, fertility often improves before significant weight loss for individuals taking GLP1 RA, therefore consideration of appropriate contraception should occur prior to prescription.
“There is no clear evidence of increased congenital anomaly in humans occurring for babies conceived whilst mothers are receiving GLP1 RA such that early termination of pregnancy would be indicated.
“Where an individual has received GLP1 RA, I agree that current evidence would suggest that they should stop taking them, and I would also recommend discussion of this with an obstetrician – given the lack of evidence of safety/harm, it would be reasonable to consider additional surveillance of the pregnancy
“I recommend that pregnancies exposed to GLP1 RA should be reported to the UKTIS (UK Teratology Information Service), or the relevant TIS of that country.
The strength of recommendation for contraception is potentially disproportionate compared to the many other medications for which there is a lack of evidence of safety/harm, however the demographic of patients receiving GLP1 RA and their potential benefits does mean that I think it is not unreasonable. However, by “planning pregnancy”, I do think that a clearer time frame for this is important – it is likely that the health benefits associated with receiving GLP1 RA with a relatively short delay to conception outweigh the risks of bariatric surgery close to conception. Ideally, I would recommend that lifestyle factors beyond just weight loss medication should be addressed to ensure a healthy pregnancy, which are more likely to be addressed through a healthcare setting (e.g. Optimisation of hypertension, safe management of cardiovascular risk factors, support to stop smoking, detection and management of glucose intolerance).”
Prof Ying Cheong, Consultant in Reproductive Medicine, University of Southampton, said:
“With the growing use of GLP-1 receptor agonists among women of reproductive age—often for non-medical, aesthetic weight loss—the MHRA’s reminder is both timely and necessary. Gastrointestinal side effects such as vomiting and diarrhoea can impair oral contraceptive absorption, increasing the risk of unintended pregnancy. Although direct evidence linking GLP-1 drugs to contraceptive failure is limited, the widespread uptake of these medications means even that small risks could translate into public health concerns, if confirmed in further studies. Patients must be supported with clear, evidence-based guidance to prevent potential avoidable reproductive consequences.
“The unregulated use of GLP-1 receptor agonists from black-market sources is a serious clinical concern. Falsified products—some containing insulin—carry unpredictable risks, including hypoglycaemia, dehydration, and compromised contraceptive reliability. These are not harmless lifestyle drugs. The public urgently needs to understand that these medications require proper medical supervision to avoid unintended harm, particularly to reproductive health.”
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
Prof Ying Cheong: No conflicts.
For all other experts, no reply to our request for DOIs was received.