Comparative Study On The Variations In Pregnant Women And Fetal Thyroid Function Induced By Iodine Supplementation During Pregnancy

Objective To study different variations in pregnant women and fetal thyroid function induced by iodine supplementation during pregnancy and assess the efficiency of iodine intake during pregnancy on fetal thyroid function.Methods Urine iodine was tested by fast urine iodine quantitative analysis method. Blood sample was collected from pregnant women at term (n=93) and from cord blood (n=91). Fifty-eight women had a regular intake of a multivitamin with iodine tablet (150ug/day) during pregnancy, and 38 took no artificial iodine supplementation. Serum total T4, total T3, T4, T3, Tg and Tg-Ab were measured by RIA (Radioimmuno assay). TSH was measured by an IRMA(Immunoradiometric assay).Results Iodine supplementation (+1) induced opposite variations in thyroid function of mother and fetus. In +1 mothers, TSH was 28.41% lower than in mothers with no iodine supplementation (p<0.05). In cord blood, on the contrary, TSH was 24.26% higher in the +1 group (p<0.01). The association between iodine supplementation and high serum TSH in neonates was further substantiated by an inverse correlation between thyroglobulin and TSH in cord blood (p<0.001), whereas no specific pattern was observed in the mothers. High serum thyroglobulin was a marker of low iodine intake in both mothers and neonates. Iodine supplementation can improve pregnant women thyroid function, but inhibit fetal thyroid function.Conclusion The fetal thyroid is more sensitive to the inhibitory effect of iodine than mother thyroid; Iodine supplementation cannot, at least in areas of mild to moderate iodine deficiency, improve fetal thyroid function.