Controlled Antenatal Thyroid Screening II: Effect of Treating Maternal Suboptimal Thyroid Function on Child Cognition

Area of Science:

• Endocrinology
• Neurodevelopmental Pediatrics
• Obstetrics

Background:

• Suboptimal gestational thyroid function (SGTF) is a concern during pregnancy.
• Previous research (CATS-I) found no difference in 3-year-old IQ between children of treated and untreated SGTF mothers.
• This study extends the follow-up to assess cognitive outcomes at 9.5 years.

Purpose of the Study:

• To evaluate the long-term impact of treating suboptimal gestational thyroid function (SGTF) on childhood cognition.
• To compare cognitive outcomes in children of mothers with SGTF (treated and untreated) versus normal gestational thyroid function (normal-GTF).
• To assess intelligence quotient (IQ), long-term memory, and motor function at age 9.5 years.

Main Methods:

• Longitudinal follow-up of children from the Controlled Antenatal Thyroid Screening (CATS) study.
• Cognitive assessments including IQ (Wechsler Intelligence Scale for Children), memory, and motor function administered by a blinded examiner.
• Logistic regression analysis to compare the odds of having an IQ < 85 across maternal thyroid function groups.

Main Results:

• No significant difference in the proportion of children with IQ < 85 between normal-GTF and combined SGTF groups (OR = 1.15; P = 0.731).
• Maternal treatment for SGTF did not significantly affect the odds of a child having IQ < 85 (untreated OR = 1.33; treated OR = 0.75).
• IQ at age 3 was a significant predictor of IQ at age 9.5, accounting for 45% of the variation.

Conclusions:

• Maternal thyroxine treatment during pregnancy does not appear to improve child cognition at age 9.5 years.
• The lack of treatment effect may be due to similar proportions of children with IQ < 85 across normal-GTF and SGTF groups.
• Cognitive development at age 3 is a strong predictor of later cognitive function.