Pregnancy is one place where the GLP-1 labels are clear. The two weight-loss drugs, semaglutide sold as Wegovy and tirzepatide sold as Zepbound, are to be stopped when a pregnancy is recognized, and both labels say plainly that "weight loss offers no benefit to a pregnant patient and may cause fetal harm" [1] [2]. The diabetes versions, Ozempic and Mounjaro, are framed differently. This page sets out what each label says. The decisions themselves, about stopping, timing and birth control, belong with your prescriber.
What each label says about pregnancy
| Drug | During pregnancy | Before a planned pregnancy | Birth-control pills | Breastfeeding data |
|---|---|---|---|---|
| Wegovy (semaglutide) | May cause fetal harm; stop when pregnancy is recognized (weight or heart use) | Stop at least 2 months before | No label warning | Injection: no data. Tablets: not recommended |
| Zepbound (tirzepatide) | May cause fetal harm; stop when pregnancy is recognized | No set lead time | May work less well for 4 weeks after starting and after each dose increase | Small study: mostly undetectable in milk |
| Ozempic (semaglutide) | Use only if benefit justifies the risk to the fetus | Stop at least 2 months before | No label warning | No human data |
| Mounjaro (tirzepatide) | Use only if benefit justifies the risk to the fetus | No set lead time | May work less well for 4 weeks after starting and after each dose increase | Small study: mostly undetectable in milk |
| Metformin | No clear link to birth defects or miscarriage in published studies | No set lead time | No label warning | Present in milk at low levels |
Current prescribing information for each drug, section 8 [2] [1] [3] [4] [5].
The difference between the two pairs comes down to what they treat. Weight loss isn't a goal in pregnancy; the Zepbound label notes that appropriate weight gain is recommended for all pregnant patients, including those with obesity [1]. Diabetes is different, because poorly controlled blood sugar in pregnancy carries its own risks to mother and baby. So the Ozempic and Mounjaro labels weigh benefit against risk rather than saying stop [3] [4]. Wegovy makes the same benefit-versus-risk call for people taking it for the liver disease MASH [2].
None of the labels has enough human data to measure a risk. Zepbound's says data in pregnant patients are "insufficient to evaluate for a drug-related risk of major birth defects, miscarriage, or other adverse maternal or fetal outcomes," and its warning rests on animal studies [1]. Wegovy's says much the same of semaglutide [2]. For the wider safety picture, see is Wegovy safe? and Zepbound side effects.
Semaglutide labels add a 2-month rule before trying
Semaglutide leaves the body slowly. Its half-life is about a week, and the Wegovy label says it stays in circulation "for about 5 to 7 weeks after the last injectable dose" at the weight-loss doses [2]. Ozempic's label puts it at about 5 weeks [3].
That's why both labels set a lead time. Wegovy's: "discontinue WEGOVY in patients at least 2 months before they plan to become pregnant to account for the long half-life of semaglutide." Ozempic's says the same, citing "the long washout period" [2] [3]. If you're planning a pregnancy, bring this up with your prescriber early, since stopping a GLP-1 has its own effects on weight; those are covered in what happens when you stop a GLP-1.
The tirzepatide labels set no lead time. Tirzepatide's half-life is shorter, about 5 to 6 days per the Zepbound label [1]; how long it lingers is covered in how long Zepbound stays in your system. Your prescriber is the one to say when to stop before trying.
Tirzepatide can make birth-control pills less reliable
This is a rule on the Zepbound and Mounjaro labels only. Tirzepatide slows how fast the stomach empties, and the label says that delay may make birth-control pills less effective. It adds that the delay "is largest after the first dose and diminishes over time" [1].
In a study of a single 5 mg dose, the peak level of the pill's estrogen fell 59% and total exposure fell 20% [1]. So for 4 weeks after starting and for 4 weeks after each dose increase, the label tells prescribers to advise people who take the pill to switch to a non-oral method or add a barrier method. It also says hormonal methods that aren't taken by mouth "should not be affected" [1] [4].
Breastfeeding: thin data, and one form to avoid
The evidence here is small. For tirzepatide, a study gave a single 5 mg dose to 11 breastfeeding women; the drug was undetectable in 164 of 171 milk samples, and the rest added up to "less than 0.02% of the maternal administered dose." There are no data on effects on the baby or on milk supply [1]. The Mounjaro label reports the same study [4].
For semaglutide, the injection labels have no human milk data [2] [3]. The Wegovy pill is the exception. Its absorption enhancer, SNAC, is present in human milk and may build up in infants, so the label tells prescribers to "advise patients that breastfeeding is not recommended during treatment with WEGOVY tablets," noting that semaglutide forms without SNAC exist [2]. Every label leaves the feeding decision to you and your clinician.
If you become pregnant while taking one
Tell your prescriber as soon as you know. The Zepbound and Wegovy labels say to stop the drug when pregnancy is recognized, and Zepbound's patient guide says to tell your healthcare provider if you become pregnant while using it [1] [2]. For Ozempic and Mounjaro, your prescriber weighs your diabetes care against the risks [3] [4].
The Zepbound and Wegovy labels both describe a pregnancy exposure registry that collects information on pregnancies exposed to the drug [1] [2]. Your prescriber can tell you how to take part. The Ozempic and Mounjaro labels list no registry.
Metformin's label reads differently
Metformin's label says limited data "are not sufficient to determine a drug-associated risk," and that "published studies with metformin use during pregnancy have not reported a clear association with metformin and major birth defect or miscarriage risk" [5]. It also notes the risks of poorly controlled diabetes in pregnancy. That doesn't make it a substitute you can switch to on your own; any change belongs with your prescriber.
Metformin is present in breast milk at low levels, with infant doses of about 0.11% to 1% of the mother's weight-adjusted dose in published studies [5].
Fertility and periods: what the labels do and don't say
The GLP-1 labels' fertility sections describe animal studies only, so they offer no human data on fertility or menstrual cycles [1] [2]. Metformin's label has one relevant line: it tells prescribers to discuss the chance of an unplanned pregnancy, because metformin "may result in ovulation in some anovulatory women" [5]. If pregnancy is on your mind either way, raise it at your next visit. More on Mounjaro's overall safety is in is Mounjaro safe?, and on Ozempic's in Ozempic safety and side effects.