Weight loss medication and pregnancy: Ozempic, Mounjaro, Wegovy and Saxenda when trying to conceive, on contraception and while breastfeeding

Why do women get pregnant unexpectedly while using Ozempic or Mounjaro?

Unplanned pregnancies during GLP-1 use have two explanations: the weight loss restores ovulation, and vomiting or diarrhoea make the contraceptive pill less reliable. Neither means that the medicine itself increases fertility.

The Belgian medicines authority FAGG issued a warning in May 2024 after accounts from women who became pregnant while taking the pill. The explanation: diarrhoea and vomiting are listed as side effects in the patient information leaflet and "reduce the reliability of oral contraceptives". If you vomit shortly after taking the pill, or have diarrhoea for days, you do not fully absorb the pill.

The second explanation is more important than it seems. In many women, overweight disrupts the hormone balance and ovulation, for example with PCOS. If you lose 10 or 15 kilos, your cycle often recovers. Someone who did not get pregnant for years and became less strict about contraception as a result is suddenly fertile after all. The medication did not do that; the lower weight did.

What does GLP-1 medication do to your fertility?

In women, GLP-1 medication can indirectly improve fertility, because weight loss restores ovulation and the cycle. There is no evidence that the medicines themselves increase or decrease fertility. That is exactly why the combination of wanting a baby and GLP-1 is so tricky: you cannot use the medicine that restores your cycle once you want to become pregnant.

In men, little has been studied. Weight loss generally improves sperm quality and testosterone levels, but there are no completed studies on a direct effect of semaglutide or tirzepatide on male fertility. The patient information leaflets contain no advice for men to stop when trying for a baby. Discuss it with your doctor if you are trying for a baby together; caution is reasonable, but there is no ban.

Trying to conceive: when do you stop semaglutide, tirzepatide or liraglutide?

If you want to have a baby, you stop semaglutide at least 2 months before you try to become pregnant, tirzepatide at least 1 month before, and liraglutide as soon as you want to conceive. The difference lies in the half-life: semaglutide stays in the blood for about a week and is only practically gone after 5 to 7 weeks, tirzepatide has a half-life of about 5 days, and liraglutide of about 13 hours.

The product information for Mounjaro states: "If a patient wishes to become pregnant or is pregnant, treatment with tirzepatide should be discontinued. Tirzepatide should be discontinued at least one month before a planned pregnancy." For Ozempic and Wegovy, the period is 2 months.

In practice, this means: you first stop the GLP-1 medicine, keep using contraception until the period has passed, and only then stop the contraception. That way you can be sure the medicine is out of your body when you become pregnant. How to approach stopping is explained in stopping Ozempic and stopping Mounjaro. Bear in mind that your appetite comes back; discuss with your doctor how to keep your weight stable in the months before and during the pregnancy.

Want to have a baby and using medication to lose weight? With medical weight loss with injections, your own doctor discusses the moment to stop and the period afterwards with you →

Became pregnant while using it: what do you do now?

If you become pregnant while using a GLP-1 medicine, you stop immediately and contact your doctor and your midwife (verloskundige) the same week. No need to panic: the data so far give no reason to regard the pregnancy as at risk, but the medicine does not belong in it.

1. Stop the injections, even if you have just injected. Do not taper off; simply stop injecting.
2. Call your doctor who prescribed the medicine. They will note it in your file and can report the pregnancy to the pharmacovigilance centre (Bijwerkingencentrum Lareb), so that more becomes known about use around conception.
3. Tell your midwife or gynaecologist at the first appointment. Mention which medicine, which dose and when you gave the last injection.
4. Pay attention to your eating pattern. Your appetite returns within a few weeks. Regular meals, protein and fibre help; gaining weight quickly is not necessary and not desirable.
5. Also using diabetes medication? Then your healthcare provider adjusts your blood sugar control, often with insulin.

Overweight in itself increases the risk of pregnancy complications such as gestational diabetes and high blood pressure. The weight you have already lost is therefore a gain for the pregnancy. Your midwife will continue to monitor your weight.

After the birth and while breastfeeding

You do not use GLP-1 medication while breastfeeding. For Ozempic, Wegovy and Saxenda, the product information says: do not use during breastfeeding, because transfer into milk has been shown in animals and data in humans are lacking. For Mounjaro, a risk to the baby cannot be ruled out; the doctor weighs up whether breastfeeding or the treatment takes priority, and in practice that means: breastfeeding first, the medicine possibly afterwards.

If you are not breastfeeding, the doctor can assess when you can start again after the birth. That moment is usually after the maternity period (kraamperiode) and after recovery, and only once you are sure you do not want another pregnancy in the short term. What you can do yourself in the meantime is covered in postpartum weight loss. In a medical weight loss with injections programme, the doctor assesses whether the medicine suits you after the breastfeeding period.

Contraception during treatment: what should you watch out for?

During treatment with a GLP-1 medicine, you use reliable contraception, and if you use the pill, you take extra care with vomiting and diarrhoea. If you vomit within a few hours of taking it, or have diarrhoea for more than a day, follow the instructions in your pill's patient information leaflet (usually: additional protection such as a condom until the complaints have passed, plus a number of days afterwards).

According to the European product information, no reduced effect of the pill is expected with semaglutide, and for tirzepatide the reduced absorption after a single dose was not found to be clinically relevant. So the practical risk lies in the side effects, not in the substance itself. If you find the pill unreliable during the build-up phase, you can consider an IUD, implant or contraceptive injection with your GP (huisarts): these are not affected by gastrointestinal complaints.

With us, the eligibility check stops if you are pregnant or trying to conceive, and the doctor offers an alternative. If you want a baby at some point in the future, you can often still be treated for a period; you plan the moment to stop together.

Want to know whether medical weight loss could be right for you? Take the eligibility check, and the doctor will assess your situation →

Frequently asked questions about weight loss medication and pregnancy

What does Ozempic do to fertility?

Ozempic does not directly increase fertility, but in women the weight loss can restore ovulation and the cycle. As a result, women who previously did not get pregnant sometimes do. In men, a direct effect has not been studied.

Who should not use Ozempic?

Pregnant women, women who want to become pregnant in the short term and women who are breastfeeding. Also people who have had pancreatitis before, have a family history of medullary thyroid cancer, have serious kidney or liver problems or an eating disorder, and young people under 18. The full list is in Ozempic side effects.

Does Ozempic affect hormones?

Ozempic acts on the gut hormone GLP-1 and indirectly on insulin. It does not directly affect sex hormones, but weight loss does change the hormone balance: less insulin resistance, often a more regular cycle. Women going through menopause sometimes notice a difference in their symptoms; read more in weight loss during menopause.

What are the long-term downsides of Ozempic?

The longest-running studies follow users for up to about four years and show no new types of side effects. Points of attention are gallstones with rapid weight loss, muscle loss with too little protein, and weight returning after stopping. The overview is in GLP-1 side effects.

Can I use Mounjaro if I want to become pregnant?

No. Stop at least 1 month before you try to become pregnant and keep using contraception until then. If you become pregnant unexpectedly, stop immediately and call your doctor.

Can I use Saxenda while breastfeeding?

No. The product information rules out use during breastfeeding, because experience is lacking and transfer into milk has been shown in animals. Discuss with your doctor when you can start after breastfeeding.

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