If you are taking Mounjaro (tirzepatide) and are pregnant, planning a pregnancy, or breastfeeding, there are important safety considerations you must be aware of. This guide summarises the current UK guidance and practical steps to take.
Is Mounjaro Safe During Pregnancy?
No. Mounjaro should not be used during pregnancy. The MHRA and the product's Summary of Product Characteristics clearly state that tirzepatide is contraindicated in pregnant women. Animal studies have shown adverse effects on foetal development, including reduced foetal growth and structural abnormalities at clinically relevant doses.
There is currently insufficient human data to determine the safety of tirzepatide in pregnancy, and it should be discontinued before conception.
Planning a Pregnancy
If you are considering becoming pregnant, the following guidance applies:
- Stop Mounjaro at least 2 months before you plan to conceive. This washout period allows the drug to clear from your system given its long half-life
- Discuss alternative weight management strategies with your GP or obstetrician for the pre-conception and pregnancy period
- Continue folic acid supplementation as recommended by NHS guidelines (400 micrograms daily)
- Inform your healthcare team about your recent Mounjaro use at your first antenatal appointment
Contraception While Taking Mounjaro
Reliable contraception is essential while using tirzepatide. Importantly, Mounjaro may reduce the effectiveness of oral contraceptive pills due to its effect on gastric emptying. The MHRA advises:
- Consider switching to a non-oral contraceptive method (such as an IUD, implant, or injection)
- If using oral contraceptives, add a barrier method for 4 weeks after starting Mounjaro and after each dose increase
- Discuss your contraceptive options with your GP or sexual health clinic
Breastfeeding
It is not known whether tirzepatide passes into breast milk. Due to insufficient safety data, Mounjaro is not recommended during breastfeeding. If you are breastfeeding and wish to start weight management treatment, discuss alternative options with your healthcare team.
Unexpected Pregnancy While on Mounjaro
If you discover you are pregnant while taking Mounjaro, stop the medication immediately and contact your GP or midwife as soon as possible. Early discontinuation minimises any potential risk. Your healthcare team can arrange appropriate monitoring and reassurance scans.
Fertility Considerations
Weight loss from Mounjaro may actually improve fertility in women with obesity-related subfertility or PCOS. This means pregnancy can occur unexpectedly, even in women who have previously had difficulty conceiving. Be especially vigilant about contraception if you are not planning a pregnancy.
For the latest guidance, consult the MHRA website or speak to your prescriber directly.