Effects of maternal iodine supplementation during pregnancy and lactation on iodine status and neonatal thyroid-stimulating hormone

Objective:To determine the iodine status in pregnant and lactating women, as well as neonatal thyroid-stimulating hormone (TSH) concentration.Study Design:Pregnant women cared at our hospital, the University Hospital in Bangkok, had routinely received 200 μg iodine tablet daily since October 2010. Urinary iodine concentrations (UICs) of 1508 pregnant and 87 lactating women and 76 offspring and breast milk iodine concentration (BMIC) (n=57) were measured. Cord serum TSH levels from hypothyroidism screening were analyzed.Result:Median UIC levels of pregnant and lactating women were 170.6 and 138.0 μg l -1, respectively. Median BMIC and infants' UIC at 2-month postpartum in iodine-supplemented group were higher than the respective values of non-supplemented group. Median cord serum TSH level obtained before iodine supplementation (n=8332) was higher than that obtained after supplementation (n=5181; 7.3 vs 5.2 mU l -1).Conclusion:Maternal iodine supplementation improved iodine nutrition in their breast-fed offspring. A trend toward declining in cord serum TSH values after iodine supplementation indicates improvement of iodine status during pregnancy.