Association between maternal hypothyroidism and autism spectrum disorders in children

BackgroundTo determine whether hypothyroidism is associated with autism spectrum disorders (ASD) and how this association is influenced by race–ethnicity, sex, and timing of exposure.MethodsA retrospective cohort study was conducted using records from 397,201 children who were delivered from 1991 to 2011 and remained health plan members from 1993 to 2014.ResultsChildren of hypothyroid women had higher ASD rates than children of women without the diagnosis (2.14 vs. 1.62/1,000 person-years; adjusted hazard ratios (adj.HR), 1.31; 95% confidence interval (CI), 1.13–1.53). This occurred in women diagnosed before as well as during pregnancy. Maternal hypothyroidism was associated with ASD for both boys (3.93 vs. 2.62/1,000 person-years; adj.HR, 1.27; 95% CI, 1.07–1.50) and girls (1.10 vs. 0.61/1,000 person-years; adj.HR, 1.51; 95% CI, 1.10–2.08). Of women with a diagnosis of hypothyroidism during pregnancy, normal thyroid-stimulating hormone (TSH) and free thyroxine (fT4) levels were not associated with an increased risk of ASD in children. Compared with white children, prenatal hypothyroidism was associated with an increased risk of ASD in children of Hispanics (adj.HR, 1.09; 95% CI, 1.01–1.17) and women of other/mixed race–ethnicity (adj.HR, 1.08; 95% CI, 1.00–1.16).ConclusionMaternal hypothyroidism is associated with ASD in children in a manner dependent on race–ethnicity. Management of maternal hypothyroidism may ameliorate the risk of ASD.