The Effect of Iodine-Containing Vitamin Supplementation During Pregnancy on Thyroid Function in Late Pregnancy and Postpartum Depression in an Iodine-Sufficient Area

The purpose of this study was to investigate the effect of iodine supplementation during pregnancy on thyroid function and also its effect on postpartum depression in an iodine-sufficient area. Healthy pregnant women were divided into three groups: group A (vitamin iodine–150) receiving vitamin containing 150 μg iodine, group B (vitamin iodine–0) receiving vitamin without iodine, and group C (no vitamin) receiving no vitamin. General information was collected by questionnaire and thyroid function was determined in the third trimester of pregnancy. Depression was assessed 1 month postpartum by the Edinburgh postnatal depression scale (EPDS). The results showed that there was no significant difference in thyroid-stimulating hormone (TSH) level among the three groups (P > 0.05). FT4 concentration was significantly lower in group A (n = 234: 10.68 pmol/L) than in group B (n = 220: 11.47 pmol/L) and group C (n = 195: 11.64 pmol/L) (P < 0.05), However, it was still within the normal range. EPDS scores obtained from group B (3.50) and group C (3.00) were similar but markedly lower than group A (5.00) (P < 0.05). Despite the difference in the EPDS score, the prevalence of postpartum depression was not significantly different among the three groups. In conclusion, 150 μg/day iodine supplementation for pregnant women in areas with adequate iodine had little effect on thyroid function in the third trimester, and serum FT4 level could not be increased. Iodine supplementation during pregnancy also had no significant effect on postpartum depression.