Mounjaro and Pregnancy: Safety Guidance for Women Planning or Expecting

Mounjaro (tirzepatide) has emerged as a groundbreaking treatment, transforming the management of type 2 diabetes and obesity. As its use becomes more prevalent, many people ask: Is this medication safe to use during pregnancy?

Understanding the risks, official recommendations, and necessary precautions is the first step toward making informed health decisions. While Mounjaro offers significant benefits for its approved indications, its use requires careful consideration in the context of reproductive health.

Article Summary:

• Mounjaro is a once-weekly injection used for weight loss and type 2 diabetes, working with your body's natural hormonal systems to help control blood sugar and reduce appetite.
• A lack of robust human data on Mounjaro’s use during a reproductive health journey means clinicians universally don’t recommend using Mounjaro when pregnant or breastfeeding.
• For those on Mounjaro who want to start a family, proactive planning in partnership with your clinician is crucial. This involves a strategy for discontinuing the medication and ensuring effective contraception until you’re ready to conceive.

What is Mounjaro (Tirzepatide)?

Mounjaro is an injectable prescription medication, administered weekly via a pre-filled injection pen. It’s approved for adults with obesity to help control appetite. Its active ingredient, tirzepatide, has a unique dual-action mechanism, mimicking two hormones: GLP-1 and GIP. By mimicking both hormones, Mounjaro enhances feeling of fullness and reduces “food noise.”

A key part of its mechanism is slowing the rate by which food leaves stomach, which helps control appetite and often leads to significant weight loss. This makes it one of the most effective weight loss treatments available, widely used for weight management.

Why pregnancy is a critical concern with Mounjaro

Pregnancy initiates a complex cascade of hormonal and metabolic changes essential for healthy fetal development. Introducing a potent medication like Mounjaro, which fundamentally alters these metabolic processes.

Understanding the science: Why Mounjaro isn't recommended during pregnancy

The consensus among healthcare professionals and regulatory bodies is unequivocal: Mounjaro (and Wegovy) should be avoided during pregnancy. This recommendation is not arbitrary; it’s rooted in the drug's powerful mechanism of action, concerning findings from animal studies, and a significant lack of safety data from human clinical trials involving pregnant individuals.

Mounjaro and fetal development

Tirzepatide works by activating GLP-1 receptors and GIP receptors, which are crucial for regulating metabolism, insulin, and appetite. During pregnancy, the body’s metabolic needs change dramatically to support fetal growth and require a carefully calibrated environment.

The intentional weight loss and altered nutrient absorption promoted by GLP-1 medicines like Mounjaro are contrary to the goals of a healthy pregnancy, which requires adequate caloric intake and steady weight gain. These effects, along with potential side effects like nausea and vomiting, could inadvertently compromise the nutrient supply essential for proper fetal development.

For clear ethical reasons, pregnant women are almost always excluded from initial clinical trials for new medications. This absence of evidence is treated as evidence of unknown risk, making discontinuation the only safe recommendation.

Potential pregnancy-related problems

There are theoretical concerns about how GLP-1 treatments might influence pregnancy outcomes. Poorly managed type 2 diabetes before and during pregnancy is a risk factor for pregnancy-related complications, including pre-eclampsia and pre-term delivery.

While Mounjaro improves blood sugar control outside of pregnancy, its powerful effects on metabolism could introduce new, unpredictable variables. The primary goal during pregnancy is stable and predictable management, which is best achieved with well-studied treatments like insulin.

When to Discontinue Mounjaro Before Pregnancy

Because tirzepatide can stay in the body for an extended period, it’s crucial to discontinue Mounjaro well before trying to conceive. The medication has a half-life of approximately five days, meaning it takes about 25 to 30 days for it to be completely cleared from your system.

To provide a safe margin, most clinicians and regulatory bodies recommend stopping Mounjaro at least one month before you start trying for a baby.

Essential contraception strategies while on Mounjaro

Guidance from the Faculty of Sexual and Reproductive Healthcare (FSRH) advises that if you are using Mounjaro, you should take extra care with contraception at certain points during treatment. [3]

Tirzepatide works slightly differently from other GLP-1 medicines and can affect how quickly food and medicines move through the stomach. Because of this, the effectiveness of oral contraceptive pills may be reduced for a short period after starting treatment or increasing your dose.

What’s recommended

If you’re using an oral contraceptive pill, the FSRH recommends:

• Using a barrier method (such as condoms) alongside your pill for four weeks after starting Mounjaro, and for four weeks after each dose increase.

Alternatively, you may wish to consider a non-oral method of contraception while using Mounjaro. These options are not affected by changes in digestion and include:

• Long-acting reversible contraceptives (LARCs), such as an intrauterine device (IUD or coil), contraceptive implant, or contraceptive injection
• Non-oral hormonal options, including the contraceptive patch or vaginal ring

If you’re unsure which option is right for you, a clinician can help you choose a method that fits your health needs and preferences.

Navigating an unplanned pregnancy while on Mounjaro

Discovering an unplanned pregnancy while taking any medication can be a source of stress. If this occurs while you are on Mounjaro, it is important to act promptly and calmly, following clear steps to protect your health and the health of your baby.

Immediate steps: Contact your healthcare provider

Take a home pregnancy test as soon as possible if you miss a period or notice symptoms that could suggest pregnancy. If pregnancy is suspected or confirmed, stop taking Mounjaro. Tirzepatide is not recommended during pregnancy and should be discontinued if pregnancy occurs.

Next, contact your healthcare provider without delay. This includes your prescribing doctor and your obstetrician or midwife. Do not wait for your next scheduled antenatal appointment. Let them know that you are pregnant and have been taking Mounjaro so they can provide personalised, time-sensitive advice on how to proceed safely.

Safely discontinuing Mounjaro

If pregnancy is confirmed, your doctor will advise you to stop taking Mounjaro immediately. Tirzepatide does not require dose tapering and should be discontinued as soon as pregnancy occurs to limit any further exposure.

You should arrange an appointment with your GP or an early pregnancy unit as soon as possible to discuss the next steps. This review will focus on your individual health needs, including blood sugar control and weight management options that are appropriate and safe during pregnancy.

Mounjaro and breastfeeding: Safety considerations

For new mothers, questions about medication safety often extend into the postpartum period, particularly concerning breastfeeding. As with pregnancy, the use of Mounjaro while breastfeeding is an area that requires extreme caution due to a significant lack of data.

Mounjaro in breast milk: Is it transferred?

Currently, it is not known whether tirzepatide is transferred into human breast milk. No studies have been conducted in breastfeeding mothers. Due to the medication's molecular size, it is theorised that only small amounts might pass into breast milk, but this can’t be confirmed without data. The potential effects of even trace amounts on a nursing infant's sensitive metabolic system are completely unknown.

Current recommendations and guidance for breastfeeding mothers

Given the lack of safety data, the official recommendation from manufacturers and regulatory bodies is to avoid using Mounjaro while breastfeeding. The potential risks to the infant, though unknown, are considered to outweigh the potential benefits to the mother. Your doctor will advise you to either discontinue breastfeeding to take the medication or continue breastfeeding and use an alternative, well-studied therapy for your own health needs.

The decision on when to resume Mounjaro after giving birth should be made in close consultation with your doctor. If you are breastfeeding, you must wait until you have completely weaned your child before resuming Mounjaro.

UK regulatory bodies and their stance

In the UK, the Department of Health and Social Care and its executive agency, the Medicines and Healthcare products Regulatory Agency (MHRA), provide definitive guidance. The MHRA explicitly advises that women should not take GLP-1 medicines like Mounjaro if they are pregnant, trying to conceive, or breastfeeding.

This stance is reinforced by the General Pharmaceutical Council, which regulates pharmacists who dispense these medications, ensuring they provide correct safety information. The advice from your clinician, GP, or specialist endocrinologist will align with official guidelines.

Conclusion

Mounjaro and pregnancy guidance can be summarised into three critical actions:

• Use effective contraception: If you are taking Mounjaro and are sexually active, you must use a reliable, non-oral form of contraception to prevent unintended exposure.
• Plan: If you wish to become pregnant, consult your doctor or clinician months in advance. It’s recommended that you stop taking Mounjaro at least one month before trying to conceive.
• Communicate immediately: If you discover you’re pregnant while taking Mounjaro, contact your healthcare provider and clinician without delay to stop the medication and establish a safe care plan.

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References

1. How does Mounjaro work for Weight Loss? [Internet]. Drugs.com. 2024. Available from: https://www.drugs.com/medical-answers/mounjaro-work-weight-loss-3570665/
2. Claire H. Parker BS, Craig Slattery PhD, Donal J. Brennan PhD, MB, Carel W. le Roux PhD, MBChB. Glucagon-like peptide 1 (GLP-1) receptor agonists' use during pregnancy: Safety data from regulatory clinical trials. Journal of Pharmacology [Internet]. 2025 May 06. Available from: https://dom-pubs.onlinelibrary.wiley.com/doi/full/10.1111/dom.16437
3. 1.GLP-1 agonists and contraception Patient information leaflet [Internet]. 2025. Available from: https://www.cosrh.org/Common/Uploaded%20files/documents/Patient-information-GLP-1-agonists-and-contraception.pdf