Iodine requirement increases during pregnancy and breastfeeding. Inadequate iodine intake during pregnancy and breastfeeding may impair thyroid hormone synthesis in both mother and fetus. Iodine supplementation may help to meet the increased iodine demand during this critical period and prevent or correct iodine deficiency and its consequences. The aim of this symposium lecture is to assess trials available on iodine supplementation and its effects on short-and long-term outcomes in pregnant and breastfed women and their children.
Pregnancy: Nine randomized clinical trials and 2 intervention studies reported the effects of maternal supplementation on maternal and neonatal iodine status and thyroid function. Four RCTs and one intervention study addressed the impact of gestational iodine supplementation on neonatal anthropometric indices at birth and infant neurocognitive development. In nearly all studies, there was improvement in maternal and fetal iodine status, however, studies on the thyroid function of pregnant women and their infants showed inconsistent results. None of the RCTs reported beneficial effects of iodine supplementation on neonatal anthropometric indices. No improvements were found in infant cognitive, language, and motor development, although there was an improvement in some motor function. Iodine supplementation before conception was more effective than during pregnancy.
Breastfeeding: A meta-analysis revealed that the iodine concentrations detected in colostrums and breast-milk samples from iodine-sufficient countries indicated the provision of adequate iodine to breast-fed infants residing in these countries. Studies have shown that supplementation of breast-feeding mothers with either 300 or 150 µg/day iodine improved maternal UIC compared to the placebo and the formula-feeding groups. However, it has been demonstrated that in iodine-sufficient areas with effective salt iodization, lactating mothers and infants have no need for iodine supplements.
Conclusions: Salt iodization is a safe, cost-effective, widely accepted and sustainable strategy for the prevention and control of iodine deficiency. Countries with well established universal salt iodization programs report great success in eliminating iodine deficiency among general populations, though this is not reflected in the most susceptible groups, namely pregnant women and lactating mothers. Although major societies have recommended iodine supplementation of 150 µg daily during pregnancy and lactation, this recommendation is effective only in areas with severe or moderate iodine deficiency. No definitive conclusion has been yet reached regarding the beneficial effects of iodine supplementation in areas of mild iodine deficiency and those with universal salt iodization program, in particular on infant growth and neurocognitive development. Further high quality RCTs with larger sample sizes are still required to gain a better understanding of these issues.