The reported link between early life exposure to acetaminophen and the development of asthma in children is “weak” and “overstated” based on currently available evidence, according to a report published by the Archives of Disease in Childhood.

In a review of currently available data culled from Embase and PubMed databases, 1,192 relevant studies conducted between 1967 and 2013 were analyzed, of which 11 were included for analysis. Of these 11 studies, 5 found “increased odds” that exposure to acetaminophen during the first trimester of pregnancy could lead to development of asthma (pooled odds ratio, 1.39); however, there was a high degree of between-study heterogeneity among the trials (I2 = 64.2%, P = .03), reported Dr. M. Cheelo of the University of Melbourne, and associates.

Of those five, only two studies examined the effects of acetaminophen exposure during the second trimester, but attained widely disparate results: Study one reported an OR of 1.06, while the other reported an OR of 2.15, with I2 = 80%. Two studies also tested acetaminophen exposure during the third trimester and found a “weak association,” with a pooled OR of 1.17. Three studies look at acetaminophen exposure through an entire pregnancy, but all had “significant heterogeneity” in their findings (OR = 1.65, 1.22, and 0.74; I2 = 89%). Only one study that was examined adjusted for respiratory tract infections during pregnancy, but according to the authors, “all studies that adjusted for early life respiratory tract infections found a reduction in the association between [acetaminophen] exposure and subsequent childhood asthma” (Arch. Dis. Child. 2014 [doi:10.1136/archdischild-2012-303043]).

The other 6 of the 11 total studies examined acetaminophen exposure over the first 2 years of life. Three of these studies found a “weak positive association,” as did four studies directly comparing children with and without acetaminophen exposure. All but one study adjusted results for respiratory tract infections during pregnancy, which caused a “moderate attenuation of the association between frequency of [acetaminophen] intake and childhood asthma.” Consequently, investigators concluded that “evidence of an association between early life [acetaminophen] and asthma is often overstated, and there is currently insufficient evidence to support changing guidelines in the use of this medicine.”

The authors reported no relevant financial conflicts of interest.