What are the outcomes for mothers and babies when women on Mounjaro (tirzepatide) conceive during treatment?

Tirzepatide (Mounjaro) in Pregnancy: Outcomes for Mothers and Babies

Tirzepatide should be discontinued before conception, as it is contraindicated during pregnancy due to potential risks of fetal abnormalities, based on animal studies showing fetal growth reductions and malformations. 1

Evidence on Maternal and Fetal Risks

The FDA label for tirzepatide (Mounjaro) clearly states significant concerns regarding pregnancy:

• Animal reproduction studies show fetal growth reductions and abnormalities at clinically relevant exposures 1
• The label specifically states: "MOUNJARO should be used during pregnancy only if the potential benefit justifies the potential risk to the fetus" 1
• In pregnant rats, tirzepatide caused increased incidences of external, visceral, and skeletal malformations at doses that are clinically relevant 1
• In pregnant rabbits, tirzepatide caused maternal mortality or abortion at all dose levels tested 1

Preconception Recommendations

For women planning pregnancy who are currently on tirzepatide:

1. Discontinue tirzepatide before attempting conception

   • Similar to other potentially teratogenic medications, a washout period is advisable
   • The FDA label recommends switching to non-oral contraceptive methods or adding barrier methods for 4 weeks after initiation and after each dose escalation 1

2. Use effective contraception while on tirzepatide

   • The drug may affect the absorption of oral contraceptives due to delayed gastric emptying 1
   • Non-oral contraceptive methods are preferred while on tirzepatide 1

Management if Pregnancy Occurs While on Tirzepatide

If a woman becomes pregnant while taking tirzepatide:

1. Discontinue tirzepatide immediately
2. Obtain urgent obstetric consultation
3. Discuss potential risks with the patient
   • Based on animal studies, there may be risks of fetal malformations and growth restrictions 1

Comparison to Other Medications with Known Teratogenic Effects

While there are no human pregnancy outcome studies specific to tirzepatide, we can draw parallels from other medications with documented teratogenic effects:

• Molnupiravir, which has shown embryo-fetal lethality and teratogenicity in animal studies, is contraindicated in pregnancy 2
• Methotrexate, a known teratogen, requires discontinuation at least 3 months before conception due to its association with increased risk of cardiovascular defects and oral clefts 3

Breastfeeding Considerations

There is insufficient data on tirzepatide use during breastfeeding. Given the concerns about potential adverse effects on infant development, breastfeeding while on tirzepatide is not recommended, similar to other medications with potential serious adverse effects on infants 1.

Clinical Decision Algorithm

1. For women currently on tirzepatide who desire pregnancy:

   • Discontinue tirzepatide
   • Use effective contraception until the drug is cleared from the system
   • Consider alternative weight management or diabetes control strategies that are pregnancy-compatible
   • Plan conception only after appropriate washout period

2. For women who become pregnant while on tirzepatide:

   • Immediately discontinue the medication
   • Obtain urgent obstetric consultation for risk assessment
   • Consider detailed fetal anatomic ultrasound to evaluate for potential abnormalities
   • Provide close maternal-fetal monitoring throughout pregnancy

Conclusion

Until human pregnancy outcome data becomes available for tirzepatide, the prudent approach is to avoid its use before and during pregnancy based on concerning animal data showing fetal abnormalities. Women of childbearing potential should be counseled about these risks and appropriate contraception while using tirzepatide.