Maternal thyroid hormone trajectories and cognitive develpoment in preschoolers: the Ma'anshan Birth Cohort

To examine the potential effect of thyroid hormone trajectories on children's cognitive development (3-6 years) and the critical period when maternal thyroid dysfunction during pregnancy might act.

Based on Ma'anshan Birth Cohort (MABC) in China, pregnant women were recruited at their first antenatal checkup from May 2013 to September 2014. A total of 1843 mother-child pairs were included in the analysis. Maternal thyroid hormones were repeatedly assayed in early, mid and late pregnancy. The dynamic changes of FT₄, TSH and T₃/FT₄ throughout pregnancy were determined by the fitting of trajectories. The Wechsler Preschool and Primary School Scale of Intelligence was applied to assess the preschoolers' cognitive development.

Maternal low FT₄ trajectories appear to be associated with a decreased risk of children's developing verbal comprehension (OR = 0.3, 95%CI:0.2-0.7) and visuospatial problems (OR = 0.5, 95%CI:0.3-0.8). In the maternal high T₃/FT₄ trajectory group, the risk of the children developing visual spatial problems appeared to be increased (OR = 1.6, 95%CI:1.1-2.4). Maternal hypothyroxinemia in mid-pregnancy appeared to be associated with an increased risk of children developing fluid reasoning problems (OR = 2.8, 95% CI: 1.2-6.6).

We found that high T₃/FT₄ trajectory might increase the risk of visuo spatial problems in preschoolers. Maternal hypothyroxinemia in mid-pregnancy may be related the elevated risk of children's reasoning problems.

The study was based on a large prospective birth cohort study platform for thyroid hormone trajectory fitting using repeated measurements in the early, mid, and late pregnancy. The low maternal FT₄ trajectory during pregnancy may be associated with children's elevated VCI and VSI scores. The high maternal T₃/FT₄ trajectory was associated with children's decreased VSI scores. Maternal hypothyroxinemia in mid-pregnancy was associated with children's decreased FRI scores. Maternal T₃/FT₄ during pregnancy may be associated with cognitive development in children. A protective effect of adequate maternal FT₄ on offspring's neurodevelopment may persist into the mid-pregnancy.