Context: Maternal hypothyroidism during pregnancy is associated with adverse neuropsychological development in the offspring.
Objective: The objective of the study was to evaluate the effect of maternal thyroid dysfunction during pregnancy on a child's attention-deficit/hyperactivity disorder (ADHD) symptoms.
Design, settings, and participants: The prospective, population-based Northern Finland Birth Cohort 1986 (9362 pregnancies; 9479 infants) included analysis of maternal TSH, free T4, and thyroid-peroxidase antibodies (TPO-Abs) from early pregnancy samples (5791 women). Teachers evaluated the children's ADHD symptoms at 8 years using the Rutter B2 scale (5131 mother-child pairs), in which a high score indicated probable psychiatric disorders and three questions focused directly on ADHD.
Main outcome measures: The odds ratios (ORs) and 95% confidence intervals (95% CIs) of child having ADHD symptoms and/or a high Rutter B2 score after exposure to increases in maternal TSH levels (after logarithmic transformation), low free T4 levels, and TPO-Ab positivity was tested with logistic regression, adjusting for maternal/family covariates. Data were stratified by the child's gender due to interaction.
Results: Among girls the odds of inattention (OR 1.18, 95% CI 1.02-1.37), high Rutter B2 total score (OR 1.23, 95% CI 1.03-1.48), and combined ADHD symptoms (OR 1.39, 95% CI 1.07-1.80) significantly increased with every natural log increase in maternal TSH concentrations. Such findings were not evident in boys. No associations were seen between ADHD symptoms and low maternal free T4 levels or TPO-Ab positivity.
Conclusions: Increases in maternal TSH in early pregnancy showed weak but significant association with girls' ADHD symptoms.