Maternal and fetal effects of acetaminophen and salicylates in pregnancy.

Salicylates have been the most widely studied of the nonnarcotic analgesics in pregnancy, and in the last 20 years evidence has accumulated indicating that their ingestion in pregnancy may have adverse effects on the mother and her child. Salicylates have been found to reduce the mean birth weight of the offspring in animal studies and in 1 human study. In the third trimester of pregnancy the maternal and fetal effects are mediated through the antiprostaglandin properties of salicylates and include prolongation of gestation and labor, increased blood loss at delivery, and increased perinatal mortality. Bleeding manifestations and withdrawal symptoms in newborn infants are associated with raised fetal blood salicylate levels. These effects of salicylates warrant routine antenatal urinary screening for salicylates in communities known to use them heavily. Adverse maternal or fetal effects form acetaminophen use in pregnancy have not been reported, but formal clinical or epidemiologic studies of its use have not been conducted.