Pregnancy is one of the clearest areas of peptide safety guidance, not because extensive human pregnancy research exists, but because the research that would be needed to establish safety generally doesn't, and precaution is the standard response to that absence.
Why Pregnancy Trials Rarely Happen
For ethical reasons, pregnant individuals are almost universally excluded from initial drug trials, meaning direct human safety data in pregnancy is typically unavailable at the time of a drug's approval, and often for a long time afterward, gathered instead through more limited post-market pregnancy registries and observational data as they accumulate over years.
What Animal Data Has Shown for GLP-1 Drugs
Animal reproduction studies for semaglutide and tirzepatide have shown potential adverse effects on fetal development at doses relevant to human use, which is the basis for current labeling recommending against use during pregnancy and recommending discontinuation for a specified period before a planned pregnancy, given these drugs' extended half-life.
Unintended Pregnancy Is a Specific Documented Concern
An additional, specific issue has been noted with GLP-1 drugs: because they can slow gastric emptying and potentially affect oral contraceptive absorption, discussed in this site's drug interaction guide, there have been reports raising questions about reduced oral contraceptive reliability during GLP-1 use, part of why some prescribing guidance recommends an additional or alternative contraceptive method during treatment.
The Situation Is Even Less Clear for Unapproved Peptides
For compounds like BPC-157, TB-500, or growth hormone secretagogues, there's essentially no formal pregnancy safety data of any kind, animal or human, making the appropriate precaution even more straightforward: without any established safety information, there's no basis for assuming a compound is safe during pregnancy, and every reason to avoid it.
What to Do
Anyone who is pregnant, trying to become pregnant, or breastfeeding should discuss any peptide use, including FDA-approved GLP-1 medications, directly with their physician before starting or continuing, given both the documented animal-study concerns for approved drugs and the complete absence of safety data for unapproved ones.
The Bottom Line
Pregnancy-related caution for peptides isn't based on documented harm in humans, it's based on the standard, conservative approach medicine takes whenever direct safety data for a specific population simply isn't available, a precaution that applies even more strongly the less overall safety data exists for a given compound.
Breastfeeding Carries Similar Uncertainty
Whether and how much of a given peptide passes into breast milk, and what effect that might have on a nursing infant, is generally unknown or very limited for most compounds discussed on this site, including approved GLP-1 drugs, where current labeling generally recommends caution and individualized discussion with a physician given the limited available data, rather than a definitive clearance either way.