Neonatal thyroid status in an area of iodine sufficiency

Iodine deficiency constitutes a public health problem in many countries worldwide. Fetal neurodevelopment is affected by maternal iodine intake. The aim of present study was to assess urinary iodine excretion (UIE) in the 3 trimesters of pregnancy and evaluate its association with newborn thyroid function in Tehran, an area of iodine sufficiency.

Based on median urinary iodine in 3 trimesters, 138 pregnant women were divided into 2 groups with UIE<150 (group I) and UIE ≥ 150 μg/l (group II). Cord blood samples of their newborns were evaluated for serum concentrations of TSH, T3, T4, free T4 (FT4), and thyroglobolin. Quartiles of UIE were also determined. Correlations between mothers' UIE and newborns' thyroid function in both groups were investigated.

Fifty-two pregnant women (38%) had median UIE<150 μg/l and 86 had (62%) UIE ≥ 150 μg/l. Median UIE in groups I and II in the 1st, 2nd, and 3rd trimesters were 125 and 212 μg/l, 97 and 213 μg/l, 93 and 227 μg/l, respectively. No significant difference was seen in thyroid function of newborns in the 2 groups. Mean concentrations of T4, T3, FT4, and TSH of newborn did not show significant difference in median UIE of mothers in various quartiles.

This study shows that newborns, irrespective of mothers' UIE, in an area with a sustained iodine supplementation program, may not be at risk of alterations in thyroid functions.