Tirzepatide pregnancy: what the label says

This article is for educational and journalistic purposes only and does not constitute medical advice. Tirzepatide is a prescription medicine. If you are pregnant, planning a pregnancy, or become pregnant while taking tirzepatide, speak with a qualified healthcare professional before changing anything about your treatment.

What the prescribing label says

The Mounjaro prescribing information states that available data on the use of tirzepatide during human pregnancy are insufficient to evaluate for a drug-related risk of major birth defects, miscarriage, or other adverse maternal or fetal outcomes^[1]. The label adds that tirzepatide should be used during pregnancy only if the potential benefit justifies the potential risk to the fetus. In practice, because tirzepatide is prescribed for type 2 diabetes and weight management, clinicians typically discontinue it when a patient becomes pregnant and switch to treatments with a better-characterised human safety record.

No boxed warning covering pregnancy appears in the Mounjaro label^[1]. The boxed warning that does appear relates to the risk of medullary thyroid carcinoma, which applies regardless of reproductive status.

What animal studies found

Because human data are limited, the prescribing label reports what happened in animal reproduction studies, which the FDA requires for all new drugs^[1]. In pregnant rats given tirzepatide at the highest test dose (0.5 mg/kg twice weekly) during the period of organ development, researchers observed increased rates of external, visceral, and skeletal malformations, as well as decreased fetal body weights. In pregnant rabbits given tirzepatide at 0.1 mg/kg, fetal weights were also reduced. In a separate study following rat pups from birth through weaning, pups born to mothers given 0.25 mg/kg had lower mean body weights throughout lactation.

The label notes that these adverse effects coincided with pharmacological effects on maternal weight and food consumption, meaning it is not straightforward to separate a direct drug effect on the fetus from one driven by the mother consuming less food. That distinction matters for interpreting risk, but it does not resolve uncertainty about human pregnancy outcomes.

The evidence gap in humans

Despite prescribing rates for GLP-1 receptor agonists in the perinatal period rising from 0.2 to 6.4 per 1,000 deliveries between 2019 and mid-2024^[2], formal safety data from controlled human studies remain absent. Most of what clinicians currently have are case series and cohort data from inadvertent early-pregnancy exposures, largely because GLP-1 class drugs delay gastric emptying and may reduce the absorption and therefore the effectiveness of oral contraceptives^[3].

A 2026 review in Current Opinion in Obstetrics and Gynecology noted that emerging human cohort data on inadvertent early-pregnancy exposure report no increased risk of major congenital malformations, which provides some preliminary reassurance^[3]. The same review called for formal pregnancy registries to fill the knowledge gap. Reassurance from inadvertent-exposure cohorts is not the same as evidence from designed safety studies, and no such trial has been completed for tirzepatide specifically.

The oral contraceptive interaction

One reason inadvertent exposure occurs is that tirzepatide slows gastric emptying. The Mounjaro prescribing information states that patients using oral hormonal contraceptives should switch to a non-oral method or add a barrier method for four weeks after starting tirzepatide and for four weeks after each dose escalation^[1]. Non-oral hormonal contraceptives, such as patches, rings, implants, and injections, are unaffected by this interaction.

The clinical implication is that women of reproductive age who are prescribed tirzepatide need a contraceptive review at the start of treatment and at each dose increase^[3]. That review is part of routine prescribing care, but the gap between label guidance and real-world practice appears to contribute to the rising rate of GLP-1 prescriptions observed during pregnancy^[2].

What happens when pregnancy is confirmed

The prescribing information does not include a single sentence advising automatic discontinuation when pregnancy is confirmed, but the risk-benefit language in section 8.1 is unambiguous: use only if the potential benefit justifies the potential fetal risk^[1]. For the approved indications (type 2 diabetes and weight management), the benefit of continuing tirzepatide specifically, rather than switching to an agent with an established human safety record in pregnancy, is difficult to justify on current evidence.

A 2025 narrative review in Best Practice and Research: Clinical Endocrinology and Metabolism concluded that preconception planning should include discussion of discontinuing GLP-1/GIP receptor agonists before attempting to conceive^[4]. For women already pregnant, the decision about what to do about glycaemic management or weight management during pregnancy belongs with the treating clinician, who can weigh the individual risks of poorly controlled diabetes in pregnancy (which include diabetic ketoacidosis, pre-eclampsia, and fetal growth abnormalities) against the absence of human safety data for tirzepatide^[1].

Can tirzepatide affect fertility?

Tirzepatide is being studied in conditions that affect fertility, including polycystic ovary syndrome, and the prescribing label section 8.3 does not flag a known adverse effect on human fertility^[1]. Early trial data suggest the drug may actually improve markers of ovulatory function in women with obesity and PCOS through weight loss and insulin sensitisation. However, a 2026 review of GLP-1 class drugs and fertility concluded that formal evidence on tirzepatide specifically is limited, and that reproductive-age women should receive counselling about contraception and preconception planning at the start of treatment^[3].

What we do not yet know

There is no completed, prospective human safety study of tirzepatide in pregnancy. Pregnancy registries, which track outcomes in people who take a drug during pregnancy, are the standard tool for building post-market safety evidence, and the tirzepatide registry data are still accumulating. The animal study findings, the contraceptive interaction, and the absence of human safety data all point in the same direction: tirzepatide is not a drug to continue into pregnancy without a specific, clinician-led reason to do so.

If you are considering tirzepatide and are of reproductive age, the most productive conversation to have is with a prescribing clinician who can address contraception, preconception timing, and what to do if pregnancy occurs. That conversation should happen before the first injection, not after.