Mild maternal thyroid dysfunction at delivery of infants born ≤34 weeks and neurodevelopmental outcome at 5.5 years.

CONTEXT

Mild maternal thyroid dysfunction during early pregnancy is associated with poor neurodevelopment in affected offspring. Most studies are population based or are smaller populations of term/late preterm infants. No studies were found that focused on more preterm infants.

OBJECTIVE

Our objective was to describe the relationship between mild maternal thyroid dysfunction at delivery of infants born ≤34 wk and neurodevelopment at 5.5 yr.

DESIGN

The study design was follow-up of women and children recruited in Scotland between 1998 and 2001.

MAIN OUTCOME

We evaluated delivery levels of maternal TSH, free T(4) (FT(4)), and T(4) and the association with McCarthy Scale scores adjusted for 26 confounders of neurodevelopment.

RESULTS

Maternal serum levels and McCarthy scores were available for 143 women and 166 children. After adjustment for confounders, there were significant 3.2, 2.1, and 1.8 point decrements, respectively, in general cognitive index, verbal subscale, and the perceptual performance subscale for each milliunit per liter increment in maternal TSH. Maternal FT(4) levels were variably associated with neurodevelopment. After adjustment, significant associations were found for the general cognitive index, motor scale, and quantitative subscale; each picomole per liter decrease in FT(4) was associated with an increase of 1.5, 1.7, and 0.9 points, respectively. Maternal T(4) levels showed little relationship with neurodevelopment. None of the women in this analysis had overt hypothyroidism, but mild hypothyroidism was evident in 27%; thyroglobulin antibody (TgAb) was ≥ 40 U/ml in 28% of the women.

CONCLUSIONS

Higher maternal levels of TSH at delivery of infants born preterm were associated with significantly lower scores on the general cognitive index at 5.5 yr.