A review of the literature on the effects of acetaminophen on pregnancy outcome.

Acetaminophen is commonly used during pregnancy. Experimental animal studies do not suggest increased malformations after therapeutic use of single-ingredient acetaminophen during pregnancy. Cohort studies in humans in which exposure is prospectively ascertained show no detectable increase in congenital malformation risk associated with single-ingredient acetaminophen use during pregnancy. A case-control study identified an association between acetaminophen use during pregnancy and risk of gastroschisis in the offspring, but the study was limited by recall bias, unblinded interviewers, possible misclassification of gastroschisis, confounding by indication, difficulty in separating out the effects of combination products, and possible selection bias. Two case-control studies failed to identify a statistically significant association between acetaminophen use during pregnancy and gastroschisis. No other malformation has been shown to be causally associated with single-ingredient acetaminophen. A reported association between pre-eclampsia, preterm birth, and acetaminophen may be explained by reverse causation. Concerns expressed about childhood asthma and prenatal acetaminophen use has been addressed in a separate review. The use of single-ingredient acetaminophen during pregnancy can be justified based on outcome data. Data on the effects of acetaminophen cannot necessarily be extended to acetaminophen combination products.