Sex-Specific Associations between Maternal Thyroid Peroxidase Antibodies and Cognitive Development in Preschool Children: A Prospective Cohort Study

Background: An association between maternal thyroid dysfunction throughout pregnancy and the subsequent risk of neurodevelopmental abnormalities in offspring has been demonstrated. However, the potential effects of maternal thyroid autoimmunity on neurodevelopment in the absence of maternal hypothyroidism remain unclear. Therefore, in this study, we explored the association between maternal thyroid peroxidase antibody (TPOAb) positivity and cognitive development in preschool children. Methods: A total of 1849 mother-child pairs were recruited from the Ma’anshan Birth Cohort (MABC) Study. During the follow-up period, an electrochemiluminescence immunoassay was used to retrospectively measure serum TPOAb levels in pregnant women. The cognitive development of preschool children was evaluated by using the Chinese version of the Wechsler Preschool and Primary Scale of Intelligence-Fourth Edition (WPPSI-IV). A growth mixture model was used to fit the trajectory of TPOAb. Multiple linear regression and logistic regression models were used to explore the associations between the developmental trajectory of TPOAb-positivity at different gestational periods and the cognitive development of preschool children by sex. Results: A total of 1849 mother—child pairs (mean [SD] age: 26.7 [3.6] years) were enrolled in the final study. Maternal TPOAb positivity in the first trimester was associated with a risk of below-average processing speed index in girls (OR: 2.07; 95% CI 1.06 to 4.01) and below-average full-scale intelligence quotient (FSIQ) in boys (OR: 2.36; 95% CI: 1.10 to 5.05). Maternal TPOAb positivity in the third trimester (T3) was associated with below-average working memory index (WMI) (OR: 2.51; 95% CI: 1.02 to 6.20) in girls. In girls, the WMI (β = −3.17, 95% CI: −5.82 to −0.52), fluid reasoning index (FRI) (β = −4.49, 95% CI: −7.18 to −1.80), and FSIQ score (β = −2.43, 95% CI: −4.77 to −0.08) decreased, whereas in mothers, the level of log-transformed thyroid peroxidase antibody (lgTPOAb) increased during pregnancy. Conclusions: Positive maternal TPOAb levels during pregnancy may be associated with poorer cognitive development in preschool children. These findings require independent confirmation in other populations.