Newborn thyroid function within the normal range was not associated with cognitive development or with maternal thyroid function, according to a recent study .
Researchers from Harvard Medical School and other sites in Boston studied children born between 1993 and 2003 at 34 weeks of gestation or older (n=500) to examine the relationship between thyroxine levels in newborns and first trimester maternal thyroid function and cognition in childhood.
The mean newborn T4 was 17.6 mg/dL, according to the researchers. Levels were 1.07 mg/dL greater in girls (95% CI, 0.38-1.76) and 0.43 mg/dL greater in infants born after longer gestation (95% CI, 0.18-0.69).
When adjusted for maternal and child characteristics, higher newborn T4 was associated with lower scores on the visual recognition memory test among infants aged 6 months (â€“0.5; 95% CI, â€“0.9 to â€“0.2), according to the researchers.
However, at age 3 years researchers did not find this association with scores on the Peabody Picture Vocabulary Test and the Wide Range Assessment of Visual Motor Ability test.
â€œIn this sample from an iodine sufficient area, first trimester maternal thyroid function did not appear to affect a newbornâ€™s thyroid function at birth, nor does lower neonatal thyroid function within the normal range impact a childâ€™s cognition,â€ Elizabeth N. Pearce, MD, assistant professor of medicine at Boston University School of Medicine, said.
These results were unexpected; we look forward to the results of trials currently ongoing in the United States and Europe to better elucidate the relationship between mild maternal hypothyroidism and child cognition.