Effects of GLP-1 on Pregnancy: What UK Women Need to Know (October 2026)

01 · The core answer

What happens if you get pregnant on a GLP-1 medicine?

If you find out you are pregnant while taking Mounjaro, stop the medicine and tell your prescriber promptly.¹³ The product information is clear that it must not be used during pregnancy.¹ Stopping is the correct first step, and you do not need to wait for a scheduled review.

A positive test after an unplanned conception is not a reason to panic. Contact your prescriber and your GP or midwife, tell them which medicine you took and roughly when your last dose was, and let them guide the next steps. Our GLP-1 pregnancy risk guide explains how clinicians approach this conversation.

Tirzepatide has a half-life of about five days, so after a final dose it takes roughly four to five weeks to clear the system. There is no way to speed this up, and nothing needs doing while it clears.¹

02 · Planning ahead

Planning a pregnancy: when to stop

Stop Mounjaro at least one month before you start trying to conceive.¹ Because the medicine takes four to five weeks to clear, build that gap into your plans rather than stopping the week you hope to conceive.

Tell your prescriber about fertility plans in your consultation, not afterwards. Our prescribing team can then plan your treatment and review dates around your timeline. If you already take a different GLP-1 medicine, its own leaflet sets the stopping advice, and your prescriber can confirm it. Our guide on being on a GLP-1 while pregnant goes deeper on this.

A free consultation reviewed by a GPhC-registered prescriber comes first.

03 · Contraception on treatment

Contraception while taking Mounjaro

Reliable contraception matters because the medicine must not be used in pregnancy, and the pill needs special attention. Mounjaro slows stomach emptying, which can reduce how well oral contraceptive pills are absorbed. The SmPC advises switching to a non-oral method, or adding a barrier method (such as condoms), for 4 weeks after starting Mounjaro and for 4 weeks after each dose increase. This applies to the pill only — implants, coils and injections are unaffected.¹⁷

Tell your prescriber which method you use and they can advise on the safest option for you.

04 · Fertility, PCOS and ovulation

Fertility, PCOS and the so-called baby boom

Weight loss can improve fertility, and unplanned pregnancies are sometimes discussed in the media as an "Ozempic baby boom". Ozempic is semaglutide licensed for type 2 diabetes — it is not a UK weight-loss medicine, and prescribing it privately for weight loss is off-label. Improving weight can restore ovulation.

Mounjaro is not licensed specifically for PCOS, but many women with PCOS meet the licensed weight-management criteria. Weight loss itself is a recommended approach that can improve insulin resistance, cycles and symptoms. Eligibility is assessed on the standard BMI criteria, and you should mention PCOS and any fertility plans in your consultation.⁴

So is it harder to get pregnant on these medicines? Nothing in the Mounjaro prescribing information says so. If your cycles become more regular, pregnancy may become more likely, which is why contraception should not be dropped just because periods were previously irregular. See our guide to GLP-1 agonists and pregnancy for related questions.

05 · Periods and IVF

Periods, IVF and new symptoms

Changes to your periods are not a listed topic in the Mounjaro prescribing information. Because weight change can alter cycles, your pattern may shift as you lose weight. Treat any new or worrying symptom as a reason to speak to your prescriber, and you can report suspected side effects through the Yellow Card scheme.¹⁹ A late period on treatment should prompt a pregnancy test, not an assumption.

There is no set IVF timetable for Mounjaro. The medicine must not be used in pregnancy, so any plan to start fertility treatment should be agreed between your fertility clinic and your prescriber in advance, with the stopping point built in.¹ Do not carry on with the pen while a cycle is under way unless both teams agree.

06 · Breastfeeding and after birth

Breastfeeding and restarting treatment

Current prescribing information indicates minimal transfer of tirzepatide into breast milk; discuss breastfeeding with your prescriber so the decision reflects your circumstances.¹ This is a conversation to have before you restart, not something to decide alone.

If you want to return to treatment after pregnancy, a fresh consultation re-checks suitability. Repeat orders with us never auto-ship, so your prescriber reviews your situation each time. For the wider picture, our Mounjaro and pregnancy guide and safety overview cover the same ground from other angles.

07 · NHS and private routes

NHS and private routes

Mounjaro is available on the NHS, but access is being phased in over several years. NICE recommends it for adults with a BMI of at least 35 plus at least one weight-related condition, and the NHS primary-care rollout began in June 2025 with the highest-need groups first (initially BMI 40+ with four or more qualifying conditions).⁴⁶ Full rollout is expected to take years, so many people who meet the licensed criteria choose regulated private treatment. Either way, pregnancy planning belongs in the first conversation. Our weight loss clinic page explains how we work, and the Mounjaro pregnancy side effects guide adds detail.