Maternal Thyroid Dysfunction During Pregnancy and Childhood Autism or Other Developmental Outcomes.

Overt maternal hypothyroidism during pregnancy has been associated with cognitive impairment in offspring, but less is known about effects of subclinical hypothyroidism and other maternal thyroid conditions on autism spectrum disorder (ASD). This study examined the relationships between maternal thyroid dysfunction during pregnancy and child neurodevelopmental outcomes. Participants were from a high ASD likelihood pregnancy cohort (MARBLES). Maternal thyroid dysfunction (hypothyroid or hyperthyroid compared to euthyroid) was measured in up to one blood sample per trimester. Thyroid stimulating hormone (TSH) and free thyroxine (FT4) were also examined as exposures. Outcomes were child ASD diagnosis, non-typical development (non-TD), typical development and standardized scores from the Social Responsiveness Scale (SRS). Outcomes were confirmed by study psychometricians. Multinomial logistic and quintile regressions were used to examine associations of maternal thyroid dysfunction (using trimester-specific reference ranges) with developmental outcomes and SRS scores. Among 285 pregnancies, 83.9% were categorized as euthyroid, 9.5% hypothyroid, and 6.7% hyperthyroid. Of 285 children included in analyses, 28.8% were diagnosed with ASD (n = 82; female = 27) and 14.7% with non-TD (n = 42; female = 19). Maternal hypothyroid conditions were associated with increased ASD:TD odds (adjusted RRR = 3.40, 95% CI: 1.22, 9.45; p = 0.02). Significant relationships were also found between hypothyroid conditions and non-TD, and between first trimester TSH and ASD. There was no evidence of a relationship between either TSH or FT4 and preschool SRS scores. Findings suggest that maternal hypothyroid conditions during pregnancy are associated with greater chances of their children developing ASD and other neurodevelopmental differences among children with high familial likelihood of ASD.