GLP-1 pregnancy and fertility

Pregnancy — contraindicated

All licensed GLP-1 receptor agonists in the UK are contraindicated in pregnancy:

• Wegovy (semaglutide)
• Ozempic (semaglutide)
• Rybelsus (oral semaglutide)
• Mounjaro (tirzepatide)
• Saxenda, Victoza (liraglutide)

The contraindication is based on animal reproductive toxicity at clinically relevant exposures and the absence of controlled human safety data in pregnancy. The relevant prescribing information requires patients to be counselled to avoid pregnancy during treatment.

Washout before planned conception

GLP-1 medicines have long half-lives:

• Semaglutide: roughly 7 days — full clearance takes weeks.
• Tirzepatide: roughly 5 days — full clearance takes weeks.
• Liraglutide: roughly 13 hours — shorter washout.

The conventional advice for semaglutide and tirzepatide is to stop at least two months before planned conception. Specific timing should come from your prescriber based on the product and your situation.

Contraception during GLP-1 treatment

Two practical issues:

1. Mounjaro and oral contraceptive absorption

Tirzepatide’s effect on gastric emptying can reduce the absorption of oral contraceptives. The prescribing information recommends barrier contraception (or switching to a non-oral method) for four weeks after starting Mounjaro and after each dose escalation. Semaglutide products carry less explicit guidance on this point but the same mechanism applies in principle.

2. Restored fertility through weight loss

Significant weight loss can restore ovulation in patients with polycystic ovary syndrome (PCOS) or weight-related anovulation. A patient who has not conceived in years may unexpectedly become fertile during GLP-1 treatment. The “Ozempic baby” anecdote in mainstream media reflects this.

The practical takeaway: patients of reproductive age starting a GLP-1 should have an explicit contraception conversation with their prescriber even if they consider themselves to have low fertility.

If you become pregnant on a GLP-1

1. Stop the medicine immediately.
2. Contact your prescriber and your GP promptly.
3. Standard early-pregnancy pathways apply (booking, dating scan).
4. The clinical team can advise on enrolling in a pregnancy outcome registry (where available) — the more reported outcomes, the better the future safety data.

Animal data is concerning but the absence of human controlled data means the management focuses on stopping the medicine and monitoring the pregnancy.

Breastfeeding

GLP-1 medicines are also not recommended during breastfeeding; it is not known whether they pass into breast milk. Discuss alternatives with your prescriber.

Fertility treatment context

Some fertility clinics advise stopping GLP-1 treatment before starting IVF or other assisted reproduction cycles. Talk to your fertility clinician — they will want a specific washout plan compatible with the cycle.