What Do the Manufacturers Say About Using Mounjaro or Wegovy During Pregnancy?
Both Eli Lilly (manufacturer of Mounjaro) and Novo Nordisk (manufacturer of Wegovy) advise that these medications should not be used during pregnancy.
Key points from manufacturer guidance include:
- GLP-1 medications are not recommended for pregnant women
- There is limited human data on the effects of tirzepatide or semaglutide during pregnancy
- Animal studies have shown potential risks to fetal development, including reduced fetal weight and developmental abnormalities at certain doses
How GLP-1 Medications May Affect Fertility and Conception
An important and often unexpected factor is that weight loss itself can influence fertility.
Potential effects include:
- Improved menstrual cycle regularity in women with obesity or PCOS
- Changes in ovulation patterns as body fat and insulin resistance decrease
- Weight loss may increase fertility, making conception more likely than before treatment
- Hormonal shifts during treatment could impact conception timing
This means some women may find they can get pregnant on Mounjaro or Wegovy even if they previously struggled to conceive. However, there are no comprehensive studies specifically examining fertility outcomes while actively using GLP-1 medications.
You can read more in our dedicated guides on Mounjaro and fertility and Wegovy and fertility.
Managing an Accidental Pregnancy While on Mounjaro or Wegovy
Weight loss itself can influence fertility, particularly for people living with obesity. You can learn more about the relationship between weight, fertility, and pregnancy in our guide on obesity and pregnancy.
Immediate steps after discovering pregnancy
If you believe you may be pregnant while taking Mounjaro or Wegovy:
- Stop the medication immediately
- Confirm the pregnancy with a home test or blood test
- Contact your healthcare provider as soon as possible
- Arrange an early prenatal appointment
- Make a note of:
- Medication name (Mounjaro or Wegovy)
- Dosage
- Duration of use
- Date of last injection
This information helps clinicians assess potential risks and plan appropriate monitoring.
Medical considerations and risks during pregnancy
Currently, there is no definitive evidence showing GLP-1 medications cause harm in human pregnancies but the absence of evidence is not the same as evidence of safety.
Medical considerations may include:
- Closer monitoring during early pregnancy
- Discussion of potential (but unquantified) fetal risks
- Managing appetite changes or blood sugar levels after stopping treatment*
- Emotional support and reassurance
Prevention Strategies for Wegovy and Mounjaro Users
If you are not planning a pregnancy, contraception is strongly recommended while using GLP-1 medications.
Effective strategies include:
- Using reliable contraception consistently
- Understanding that weight loss can increase fertility
- Considering contraception options that don’t rely solely on absorption through the gut
Contraception Effectiveness While on Mounjaro and Wegovy
When taking GLP-1 medications such as Mounjaro or Wegovy it’s important to consider how they may affect contraception, particularly for women of reproductive age who do not wish to become pregnant.
Mounjaro and Contraception
Women should use effective contraception while treated with tirzepatide.
- Consider switching to a non-oral contraceptive method such as an:
- Intrauterine device (IUD)
- Contraceptive implant
- Patch or vaginal ring
- If staying on an oral contraceptive, add a barrier method (e.g. condoms) during:
- the first 4 weeks after starting tirzepatide, and
- the first 4 weeks after each dose escalation.
This approach helps mitigate the theoretical risk that tirzepatide could impair oral hormone absorption due to delayed gastric emptying or other GI effects.
If pregnancy is planned, tirzepatide should be discontinued at least 1 month before attempting conception.
For more detailed guidance, read our full article on Mounjaro and contraception, including how dose changes may affect contraceptive effectiveness.
Wegovy and Contraception
Semaglutide is not expected to decrease the effectiveness of oral contraceptives. We also cover this in more detail in our guide on Wegovy and contraception, including what to do if gastrointestinal side effects occur. However:
- Women of childbearing potential are still advised to use contraception during treatment with Wegovy.
- Because semaglutide therapies, like other GLP-1 agonists, can cause gastrointestinal side effects (nausea, vomiting, diarrhoea), these symptoms may temporarily interfere with absorption of oral contraceptive pills. In such cases standard “missed pill” or contraceptive guidance should be followed.
Unlike tirzepatide, there is no specific requirement with Wegovy to add barrier methods or switch from oral methods simply because of drug absorption concerns, as semaglutide does not have a clinically relevant effect on contraceptive hormone levels.
If pregnancy is planned, semaglutide should be discontinued at least 2 months before attempting conception due to its long half-life.
Key Takeaways
- You should not take Mounjaro or Wegovy while pregnant
- If you accidentally get pregnant on Mounjaro or Wegovy, stop treatment and seek medical advice immediately
- Weight loss from GLP-1 medications may increase fertility
- Human safety data is limited, but monitoring and support are available
- Reliable contraception is essential if pregnancy is not desired
If you have concerns about pregnancy, fertility, or GLP-1 medications, contact the team at Phlo Clinic. We’re here to support you every step of the way with personalised, expert guidance.
For those thinking ahead to life after pregnancy, we also share guidance on post-partum weight loss and returning to treatment safely where appropriate.
References
- Electronic Medicines Compendium (eMC). Wegovy 2.4 mg solution for injection in pre-filled pen – Summary of Product Characteristics (SmPC). Novo Nordisk Ltd.
Available from: https://www.medicines.org.uk/emc/product/13799/smpc - Electronic Medicines Compendium (eMC). Mounjaro 2.5 mg–15 mg solution for injection in pre-filled pen – Summary of Product Characteristics (SmPC). Eli Lilly and Company Limited.
Available from: https://www.medicines.org.uk/emc/product/15481/smpc - Eli Lilly and Company. Mounjaro (tirzepatide): Pregnancy and contraception considerations. Data on file and prescribing information referenced via UK SmPC.
- Novo Nordisk. Semaglutide (Wegovy): Use in women of childbearing potential and pregnancy. Prescribing information referenced via UK SmPC.
- Faculty of Sexual & Reproductive Healthcare (FSRH). Drug interactions with hormonal contraception. Clinical guidance on factors affecting oral contraceptive absorption.
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