Use of acetaminophen (paracetamol) during pregnancy and the risk of autism spectrum disorder in the offspring.

Acetaminophen (paracetamol) is available over the counter in most countries and is widely considered to be safe for use during pregnancy; studies report gestational exposures to acetaminophen that lie in the 46%-65% range. Acetaminophen influences inflammatory and immunologic mechanisms and may predispose to oxidative stress; these and other effects are hypothesized to have the potential to compromise neurodevelopment in the fetal and infant brain. Two ecological studies suggested that population-level trends in the use of acetaminophen were associated with trends in the incidence/prevalence of autism; one of these studies specifically examined acetaminophen use during pregnancy. One large prospective observational cohort study found that gestational exposure to acetaminophen (especially when the duration of exposure was 28 days or more) was associated with motor milestone delay, gross and fine motor impairments, communication impairment, impairments in internalizing and externalizing behaviors, and hyperactivity, all at age 3 years; however, social and emotional developmental behaviors were mostly unaffected. A very recent large cohort study with a 12.7-year follow-up found that gestational exposure to acetaminophen was associated with an increased risk of autism spectrum disorder, but only when a hyperkinetic disorder was also present. In the light of existing data associating acetaminophen use during pregnancy and subsequent risk of attention-deficit/hyperactivity disorder, this new finding suggests that the predisposition, if any, is toward the hyperkinetic syndrome rather than to autism. In summary, the empirical data are very limited, but whatever empirical data exist do not support the suggestion that the use of acetaminophen during pregnancy increases the risk of autism in the offspring.