GLP-1s and pregnancy: the two-month wash-out you need to plan for

What the labels say

The prescribing information for both semaglutide (Wegovy, Ozempic) and tirzepatide (Zepbound, Mounjaro) carries the same instruction:

Discontinue use at least 2 months before a planned pregnancy.

This is a precautionary recommendation, based on two things. First, animal reproductive studies have shown reduced foetal weight, structural abnormalities, and other developmental signals at clinically relevant doses. Second, GLP-1 medications have long half-lives, about a week, and full clearance from the body takes roughly five half-lives, or five weeks. The two-month window builds in a margin.

The same labels list pregnancy under "Special Populations" and note that the available human data is insufficient to determine drug-associated risk. (Wegovy label, Section 8.1.)

What the animal data actually showed

Reproductive toxicology studies in rats and rabbits, submitted as part of the FDA approval packages, showed signals at doses comparable to or higher than human therapeutic doses:

• Semaglutide: Reductions in foetal body weight, increases in skeletal variations, and in some studies, signals of embryotoxicity.
• Tirzepatide: Similar foetal weight reductions and some external, visceral and skeletal malformations at higher exposures.

Animal data does not always translate to humans, and these were not catastrophic findings, they were the kind of signal that triggers a precautionary stance in the absence of human evidence. Until larger human registries report out, the precautionary stance holds.

What the early human data shows

The available human data, as of 2026, is reassuring but limited. A series of registry studies and post-marketing surveillance reports (notably from the U.S. and Israeli health systems) have looked at women who became pregnant while on semaglutide. The largest published analysis followed several hundred pregnancies and did not detect a meaningful increase in major congenital malformations compared with matched controls. (Cesta CE et al., JAMA Intern Med 2024.)

This is comfort, not a guarantee. Several thousand more pregnancies need to be studied before the answer is settled. Until then, the conservative recommendation stands: do not plan to be pregnant on a GLP-1.

What to do if you are trying to conceive

A practical sequence, often used in fertility-aware prescribing:

1. Reach your goal weight (or a stable, sustainable weight) before stopping. Weight loss before conception improves fertility outcomes in most women with overweight or obesity, including ovulation regularity and reduced gestational diabetes risk.
2. Stop the GLP-1 at least 8 weeks before attempting conception. Confirm a plan for contraception during the wash-out.
3. Have a maintenance plan. Without the drug, hunger returns. Some women regain meaningfully in the months between stopping and conceiving. A nutrition plan, focused on protein, fibre, and consistent meal structure, is the bridge.
4. Schedule a preconception visit with your OB-GYN. Discuss any other medications, prenatal vitamins, folate intake, and management of any underlying conditions (PCOS, type-2 diabetes, hypertension).

What to do if you find out you are pregnant on a GLP-1

This is more common than people think. A meaningful share of unintended pregnancies on tirzepatide may relate to the contraception interaction we covered separately.

The right sequence:

1. Stop the medication immediately. Do not take the next weekly dose.
2. Call your prescriber and your OB-GYN today. Both, not one. Each has a different part to manage.
3. Do not assume the worst. As discussed above, the early human data has not shown a strong signal of harm. Your prescriber will want to know exactly when conception likely occurred, what doses you were on, and your full medical history.
4. Be honest with your maternal-foetal medicine team if you are referred to one. The data is what it is, and your care team needs to know it accurately.

After delivery

GLP-1 medications are not recommended during breastfeeding. The Wegovy and Mounjaro labels both note that semaglutide and tirzepatide are present in the milk of lactating animals, and human milk data are limited. The decision to restart a GLP-1 while breastfeeding should be made with your prescriber and your paediatrician, weighing the importance of the drug to the mother against the unknowns to the infant.

For most women, the practical pattern is: deliver, breastfeed for the planned duration, and restart the GLP-1 after weaning if it remains clinically appropriate.

What to do with this

This is one of the situations where the calculator refuses to produce a deficit. Tick the box and it shows your maintenance level and the derivation instead, with no meal plan and no target, because a calorie target is not the thing you need from a website here.

See what it does show

Sources

1. FDA Prescribing Information, Wegovy. Section 8.1, Pregnancy. Label
2. FDA Prescribing Information, Mounjaro. Section 8.1. Label
3. Cesta CE et al. GLP-1 Receptor Agonist Exposure in Early Pregnancy and Risk of Major Congenital Malformations. JAMA Intern Med 2024. JAMA
4. ACOG. Pregestational diabetes mellitus, practice bulletin. ACOG

Medical disclaimer: Decisions about pregnancy and medication belong with your prescriber and your OB-GYN. This article is educational only. See our full medical disclaimer.