Iodine metabolism and thyroid function during the perinatal period: Maternal-neonatal correlation and effects of topical povidone-iodine skin disinfectants

Abstract

An adequate maternal iodine intake during pregnancy and lactation is essential for growth and mental development in fetuses and newborns. Both deficient and excess iodine may disrupt normal thyroid function. There are limited data on perinatal iodine metabolism in mothers and infants, as well as the effect of povidone-iodine (PVP–I) antiseptics used in Cesarean delivery. The urinary iodine concentration (UIC), serum iodine, thyrotropin (TSH), free thyroxine (FT4) and breast milk iodine concentration (BMIC) were measured consecutively in a total of 327 mothers and 249 term-infants in two prospective studies. The maternal median UIC was 164 µg/L in the third trimester, increased to 256 µg/L on postpartum day 2, then decreased to 116 µg/L one month later. The BMIC on postpartum days 2 and 30 was 17.6 and 13.5 µg/100g, respectively. In neonatal infants born to the mothers unexposed to PVP-I, the median UIC was 131 µg/L in the first voiding urine and increased to 272 µg/L on day 4, then slightly decreased to 265 µg/L on day 28 suggesting sufficient iodine reserve at birth. PVP-I antiseptics containing 1g of iodine for skin preparation at Cesarean delivery transiently increase maternal serum iodine concentration, UIC and BMIC, however, it has little effect on maternal TSH, FT4 and neonatal UIC, TSH, or FT4. The iodine status of pregnant women and their infants was adequate in this population; however, the UIC in lactating mothers at one postnatal month was low enough to suggest iodine deficiency or near iodine deficiency. Further studies are necessary. This study was not registered to any clinical trials registry (CTR).