Does Mounjaro affect pregnancy?
If you’re hoping to get pregnant soon, you may be wondering how Mounjaro (tirzepatide) will affect your chances of conceiving. The same applies if you’re already pregnant or breastfeeding—is the medication safe at these times? What about if you’re looking to avoid a pregnancy?
Since many of Mounjaro’s users are women of reproductive age, there are plenty of people out there with similar questions.
Can you take Mounjaro while pregnant?
The short answer is no. Mounjaro hasn’t been tested on pregnant women, so we don’t know whether there are any risks to an unborn baby. In animal studies, it has been linked to a slightly increased risk of birth defects and low birth weight. Although animal studies don't necessarily represent what would happen in people, there is not enough research on humans to suggest Mounjaro is safe to use in pregnancy.
You should stop taking Mounjaro as soon as you see that faint line on the pregnancy test—and talk to your doctor and antenatal clinic about the next steps. Better still, stop beforehand. Weight loss during pregnancy isn’t recommended anyway, so there wouldn’t be much reason to take Mounjaro pregnant even if it were 100% safe.
What if I accidentally took Mounjaro before knowing I was pregnant?
If you've discovered you're pregnant after already taking Mounjaro, don’t panic too much. Research into this area is still emerging, and effects of Mounjaro on early pregnancy are still not clear.
That said, you should still take immediate action. Here's what you should do if you accidentally took Mounjaro while pregnant:
- Stop taking Mounjaro immediately.
- Contact your healthcare provider as soon as possible.
- Schedule a prenatal appointment to confirm your pregnancy and discuss next steps, including informing them that you have taken Mounjaro.
- If you have diabetes, discuss alternative management strategies with your doctor.
- Be honest with your healthcare providers about how long you were taking Mounjaro.
How long before pregnancy should you stop Mounjaro?
The NHS recommends stopping Mounjaro at least a month before pregnancy, (and doctors in the US recommend two months).
That’s because, tirzepatide, the active ingredient in Mounjaro, takes up to 30 days to leave your system, meaning it could affect the foetus if you got pregnant in that time.
Can I get pregnant sooner if I stop Mounjaro earlier?
Mounjaro doesn't appear to reduce fertility or make it harder to conceive once it's out of your system. The one-to-two month waiting period is specifically designed to prevent any potential exposure of the embryo to the medication during early development.
There's no evidence suggesting that stopping Mounjaro earlier than planned will enhance fertility or allow you to conceive sooner than the recommended waiting period.
Does Mounjaro help with pregnancy?
You may have heard that Mounjaro could boost the chances of getting pregnant. There are lots of reports about women who struggled with fertility issues for years, only to find they got pregnant when losing weight on Mounjaro.
To begin with the bad news—we don’t yet know whether Mounjaro has any effect on fertility. But we do know that weight loss (among those who struggle with their weight) can often make it easier to get pregnant. Being a healthy weight is also associated with healthier pregnancies, lowering your risk of complications like gestational diabetes and pre-eclampsia.
What’s more, some researchers think GLP-1 drugs (the class of drugs that includes Mounjaro) might improve fertility among women with polycystic ovary syndrome (PCOS). As well as boosting insulin sensitivity, these drugs might also tackle the hormonal imbalances that interfere with ovulation.
Can you take Mounjaro while breastfeeding?
Current guidance and manufacturer advice say no — Mounjaro is not recommended while breastfeeding. It hasn’t been directly studied in breastfeeding individuals, so we don’t know if it passes into breast milk, how it might affect your baby, or whether it could impact your milk supply. Until more safety data is available, it's best to avoid using Mounjaro while breastfeeding.
Does Mounjaro pass into breast milk?
There's limited research on whether Mounjaro (tirzepatide) passes into breast milk. Based on what we know about similar medications, it's theoretically possible that small amounts could transfer to breast milk.
However, the active molecule in Mounjaro is probably too large to enter breast milk in large quantities, and the baby is unlikely to absorb it well. But since we don’t have a full picture of the risks yet, you shouldn’t take Mounjaro if you’re breastfeeding.
When can I restart Mounjaro after breastfeeding?
You can typically restart Mounjaro once you've completely finished breastfeeding. The timing should be discussed with your healthcare provider, who can assess your individual situation.
Many women experience weight retention after pregnancy, and your doctor might recommend waiting until your postpartum body has stabilised, usually around 3 to 6 months after delivery or after weaning.
This allows your hormones to normalise and gives you time to establish healthy eating and exercise habits. Your provider may also suggest alternative weight management approaches initially, gradually transitioning to Mounjaro if appropriate for your health goals.
Does Mounjaro affect your menstrual cycle?
There are no formal studies directly linking Mounjaro to menstrual cycle changes, but some users have reported irregular or unexpected bleeding. If you have PCOS, you may already experience infrequent or absent periods. Since Mounjaro can improve insulin sensitivity and support weight loss, it may help restore ovulation and bring more regularity to your cycle over time.
However, several other factors may influence your periods while on Mounjaro:
- Oral contraceptives: Mounjaro may reduce the absorption of oral contraceptive pills—particularly around the time of dose changes. This could result in hormonal fluctuations and changes to your bleeding pattern.
- Oral HRT (Hormone Replacement Therapy): Mounjaro slows down how your stomach empties, which can reduce how well your body absorbs oral HRT. This may affect any hormonal component, but is particularly important if you're taking oral progesterone, which protects the lining of your womb. Reduced absorption can lead to breakthrough bleeding or make your HRT less effective. If you're on oral HRT and are starting, changing to, or increasing the dose of weight loss injections like Mounjaro, it's important to speak with your GP or HRT provider beforehand. They may recommend switching to a non-oral route, such as patches or gels, to ensure your HRT remains safe and effective throughout treatment. Any unexpected bleeding should be reported to your GP or HRT provider.
- Weight loss: Rapid or significant weight loss, a common effect of Mounjaro, can also temporarily disrupt menstrual cycles. If you notice significant or prolonged changes to your cycle, it’s a good idea to speak to your GP, particularly if you're on hormonal contraception or HRT.
Does Mounjaro affect birth control?
Yes, Mounjaro can potentially affect the absorption of oral contraceptives. It slows down how quickly your stomach empties, which may reduce how well oral contraceptive pills are absorbed—especially around the time of a dose change.
Because of this, you must use a barrier method (such as condoms) alongside your oral contraception for the first four weeks after starting Mounjaro or after each time your dose is increased. Since Mounjaro is taken weekly and dose increases can happen monthly, some people may need to use extra protection (e.g., condoms) for extended periods during their treatment.
If you remain on the same dose for more than four weeks (for example, if you stay on the 5 mg dose for two months), you do not need to continue using additional contraception beyond the first four weeks at that dose. However, if you increase your dose again (e.g., from 5 mg to 7.5 mg), you will need to use barrier protection again for another four weeks.
So, it may be easier and more reliable to switch to a non-oral contraceptive method, such as the coil, implant, or injection, during your treatment. Speak to your GP to discuss the best non-oral contraception option for you.
Conclusion
If you’ve had a positive experience with Mounjaro so far, it can be disheartening to think about stopping if you get pregnant. Pregnancy and the postpartum period can be a tricky time from a body image perspective, and if you’ve had to pause Mounjaro, that could add another challenge into the mix.
All this said, if Mounjaro is medically recommended for you, there will be ample opportunity to re-start in future. In the meantime, the priority is to keep yourself and your baby as safe as possible.
And if you’re not pregnant yet, but would like to be, Mounjaro may well prove helpful (see if Voy’s weight loss programme might be right for you). While there are a lot of unknowns here, clearer answers are likely to emerge over the years ahead. In the meantime, it’s wise to prioritise your health—whatever that looks like for you—before embarking on your pregnancy journey.
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