Pregnancy planning on a GLP-1: the semaglutide wash-out, the tirzepatide contraception warning, and what to do if you are already pregnant

Two facts drive everything in this guide. Semaglutide stays in the body for weeks after the last dose, and the labels ask for a two-month gap before conception because of it. Tirzepatide makes oral contraceptives less reliable for a month after starting and after every dose increase, and the labels ask for a back-up method because of that. Everything else here is detail, but the detail matters because the two drugs are different and people assume they are the same.

Semaglutide: the wash-out

The Wegovy and Ozempic labels both say, in section 8.3: discontinue in patients at least 2 months before a planned pregnancy because of the long half-life (Wegovy's wording) or long wash-out period (Ozempic's) of semaglutide. The Wegovy label's clinical pharmacology section gives the elimination half-life as approximately 1 week and states that semaglutide will be present in the circulation for about 5 to 7 weeks after the last dose. Two months is that figure, rounded up.

Section 8.1 of the Wegovy label says: available data in pregnant patients are insufficient to establish a drug-associated risk; weight loss offers no benefit to a pregnant patient and may cause fetal harm; when a pregnancy is recognised, advise the patient of the risk; discontinue Wegovy in pregnant patients who are using it for weight reduction. Animal studies at clinically relevant exposures showed fetal effects that the label attributes at least in part to reduced maternal weight and food intake.

Practically: if you intend to try to conceive in a given month, the last injection is two months before that. For someone using Wegovy for weight loss, that means a period of at least two months, and then the whole of pregnancy, off the drug. The stopping guide is about what happens to weight in that time; the short version from the trials is that it comes back, and the pregnancy-planning conversation should include a plan for that period rather than pretending it will not.

Tirzepatide: contraception, and no stated wash-out

The Zepbound and Mounjaro labels handle pregnancy differently. Section 8.1 says available data with tirzepatide in pregnant patients are insufficient to evaluate for drug-related risk, that based on animal studies there may be risks to the fetus, and describes fetal growth reductions in rats and rabbits at exposures associated with maternal weight loss. It does not contain a "discontinue X months before" instruction, and it does not contain an instruction to discontinue on recognition of pregnancy in the way the Wegovy label does, though weight loss in pregnancy is not a goal and a prescriber will almost certainly stop it.

Section 8.3 is about contraception: use of the drug may reduce the efficacy of oral hormonal contraceptives due to delayed gastric emptying, an effect that is largest after the first dose and diminishes over time. The instruction is to advise patients using oral hormonal contraceptives to switch to a non-oral method, or add a barrier method, for 4 weeks after initiation and for 4 weeks after each dose escalation. Hormonal contraceptives not taken by mouth (implant, injection, patch, ring, hormonal IUD) are not affected.

Two things follow. A person on tirzepatide who is relying on the pill and does not want to become pregnant needs a second method for the first month and for the month after every step up the escalation ladder, which on the label schedule is most of the first five months. And a person on tirzepatide who does want to become pregnant has no label number for how far ahead to stop; the label gives the elimination half-life as approximately 5 to 6 days, shorter than semaglutide's, but "shorter" is not a plan. Ask the prescriber for a date.

The Wegovy label does not carry the oral contraceptive warning; the interaction is described for tirzepatide specifically.

If you find out you are pregnant while on the drug

Stop and call the prescriber the same day. The Wegovy label's instruction is to discontinue in pregnant patients using it for weight reduction; for tirzepatide the prescriber will make the same call. Do not take a further dose while waiting for the appointment. Tell the obstetric team at the first visit exactly what you took, at what dose, and the date of the last injection; with semaglutide's half-life, exposure continues for weeks after that date and they will want it in the record.

Then consider the registry. Both labels describe a pregnancy exposure registry that monitors outcomes in women exposed during pregnancy, with a phone number in section 8.1. Enrolment is voluntary and is how the "insufficient data" in the labels eventually becomes sufficient.

Do not panic-read animal data. The labels describe findings in rats and rabbits at exposures that also caused maternal weight loss, and say the background risk of major birth defects in the general population is 2 to 4 percent and of miscarriage 15 to 20 percent regardless of any drug. Human data are limited, which is different from human data being alarming. This is a conversation with an obstetrician, not a forum.

Fertility

Neither label makes a fertility claim. Weight loss in people with obesity can restore ovulation in some who were not ovulating, which is a reason pregnancies happen on these drugs to people who did not expect them, and a second reason the contraception warning matters. That observation is general reproductive medicine, not label content.

Breastfeeding

The Zepbound label (section 8.2) reports a single-dose clinical lactation study in which tirzepatide concentrations in breast milk were undetectable or low compared with the maternal dose, and states there are no data on the effects on the breastfed infant or on milk production. The Wegovy label says there are no data on the presence of semaglutide in human milk, its effects on the breastfed infant, or its effects on milk production. Both labels leave the decision to a clinical judgement of the developmental and health benefits of breastfeeding against the mother's need for the drug and any potential effect on the infant. There is no label endorsement of use while breastfeeding for either drug.

Men

The labels contain no instruction for men planning to father a child. The Zepbound label's animal fertility data concern rats and are summarised in section 13.1. Absence of an instruction is not evidence of safety, but there is no wash-out request for men on any of the four labels.

Planning checklist

Tell the prescriber you are planning a pregnancy, ideally before you start the drug, and certainly the moment the plan forms. Agree a stop date: for semaglutide the label gives at least two months before trying; for tirzepatide, a prescriber's date. Agree a weight-maintenance plan for the gap and for pregnancy, since the trials show regain after stopping. If on tirzepatide and the pill, use a second method for four weeks after starting and after each increase, per the label, until you have stopped for pregnancy. Record the date of the last injection somewhere the obstetric team will see it. Consider the registry if exposure happens.

Compounded products

Compounded semaglutide and tirzepatide are not FDA approved and are not interchangeable with brand products; there is no pregnancy, lactation or contraception data for any compounded product. The active ingredients carry the same half-lives and the same mechanisms, so the label wash-out and contraception language above is the only guidance that exists, and a prescriber should apply it. FormBlends describes what its pharmacies dispense on its semaglutide and tirzepatide pages. Tell any prescriber, compounding or otherwise, about pregnancy plans before the first dose.