In 1990 the Food and Drug Administration (FDA) issued the following warning about aspirin use during pregnancy: "It is especially important not to use aspirin during the last three months of pregnancy, unless specifically directed to do so by a physician because it may cause problems in the unborn child or complications during delivery."

Aspirin is listed on the California Environmental Protection Agency (CAL/EPA) Proposition 65 list of developmental toxins (CAL/EPA Proposition 65 List). A developmental toxin is a substance that an expert group of scientists found sufficient evidence of possible harm to unborn children. The FDA warning is included in the CAL/EPA listing.

Aspirin and Breast Feeding

Aspirin is transferred to breast milk and it is estimated that a nursing baby receives about 4-8% of the mother’s dose (WHO 1988). Continued exposure to small doses of aspirin may be harmful to babies because aspirin tends to build up in their bodies (Findlay et al. 1981). In some countries, nursing woman are advised against aspirin use because of the possible development of Reye’s Syndrome in their babies (WHO 1988). Reye’s Syndrome is a rare condition that affects the brain and liver and is most often observed in children given aspirin during a viral illness (National Reye's Syndrome Foundation). Because sufficient information is not available to accurately determine the extent of aspirin accumulation in babies and the resulting health outcomes, the World Health Organization (WHO) Working Group on Human Lactation considers aspirin intake by nursing mothers as unsafe (WHO 1988).