Doctors should take contraception and pregnancy into account when prescribing GLP-1 medicines to patients of reproductive age, a Perth doctor who specialises in treating obesity has said.
The call comes in light of a study that found a lack of effective contraception use among women using GLP-1 medications such as Ozempic and Wegovy.
The research, published in the Medical Journal of Australia, found a significant rise in prescriptions for women without a type 2 diabetes diagnosis and raised concerns about the low use of contraception and subsequent risk of unintended pregnancies.
Originally developed for managing type 2 diabetes, such medications have become widely used for their weight-loss effects.
Dr Mark Mellor, a GP and lead clinician at Perth Weight Clinic and lead of the RACGPs specific interest group on obesity said the increased use for such purposes was not surprising given many had now been given specific indication for chronic weight management.
The new study, authored by researchers from the universities of Adelaide and Sydney as well as Monash and Flinders universities, documented 232 pregnancies within six months of GLP-1 receptor agonist initiation among the women tracked.
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The authors considered this “not infrequent” given the potential risks and the limited human data on the drugs’ effects on developing foetuses.
The study, which analysed data from more than 1.6 million Australian women aged 18-49, also showed a dramatic increase in prescribing, especially for non-diabetic women.
More than 90% of the women first prescribed GLP-1 medications in 2022 did not have a diabetes diagnosis.
Despite known risks associated with GLP-1 receptor agonists during pregnancy, primarily from animal studies showing potential for birth defects and foetal harm, the research found that fewer than one in four women (21.2%) had documented use of highly effective contraception at the time of their first prescription.
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“Clinicians need to be aware that the GLP-1 medicine is a category D for pregnancy, which means that they are known to cause foetal malfunctions in the animal models, so they should not be used in pregnancy. That also is the case with breastfeeding,” Dr Mellor said.
“We need to be mindful that many of our patients will be fertile females in the reproductive years, they might be wanting to improve their health for conception and many of them may not be on a contraceptive.
“If they may be actively planning pregnancy we need to be absolutely explicit in the information we give to our patients, that we shouldn’t be using them in those cases.
“The study shows there are women getting pregnant while taking these drugs, albeit in small numbers. We just wonder whether there was an opportunity missed to help support that woman and prevent this situation from arising.”
Dr Mellor said GLP-1s can affect the absorption of the oral contraceptive pill/
“We would always advise women that are taking the oral contraceptive pill that these medicines can decrease the dose, so they must use extra protection, like barrier methods in particular, when they are in that phase starting the medication or increasing the dose,” he said.
“What this study alluded to is the fact that actually many women are not on contraceptives when they start these treatments and I think that’s why the concern is primarily that we have women using these medicines but at risk of an unplanned pregnancy, or possibly even a planned pregnancy but unaware that these medicines are category D.”
Dr Mellor said doctors needed to ensure patients were aware of the interval of time there should be between taking these medications and getting pregnant.
“If you look at guidance on specific drugs like to Tirzepatide (Mounjaro) and Wegovy (semagutide) then there needs to be a washout period before a planned conception. For Mounjaro it’s one month and Wegovy it’s two months.”
He said best practice would be for prescribing doctors to always ensure they have that conversation with women about the risk these medicines pose to a pregnancy and encouraging the use of contraceptives.
The study authors also emphasised that even a modest weight loss from these drugs could increase fertility, making unintended pregnancies a significant risk for those not using contraception.
The researchers suggested the development of comprehensive recommendations to support the safe and effective use of these medications, stressing that conversations about reproductive health and contraception must be a routine part of every consultation when these drugs are prescribed to women of reproductive age.
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