Iodine Requirements in Pregnancy

Abstract

Iodine is an essential micronutrient required for thyroid hormone production. Thyroid hormone is critically important for growth and development, especially in utero and in early childhood. Pregnant women have increased iodine requirements of 220--250 $μ$g/day. Maternal iodine deficiency during pregnancy can have adverse obstetrical effects such as miscarriage, prematurity, and stillbirth, as well as adverse effects on offspring development including low birth weight and head circumference, and lower intelligence quotient (IQ). Worldwide, universal salt iodization is the mainstay of iodine deficiency disorder elimination efforts. Maternal iodine supplementation prior to conception or in early gestation is beneficial to prevent the adverse effects of iodine deficiency, especially in severely iodine-deficient areas. Meta-analyses of studies of maternal iodine supplementation in moderately to severely iodine-deficient areas have shown benefits for child development and cognitive function, although more research is warranted. Maternal iodine excess in pregnancy can also adversely affect maternal and offspring thyroid function. The United States is considered generally iodine sufficient, but pregnant women in the USA have been mildly iodine deficient in recent years. To prevent adverse effects of iodine deficiency, women are currently advised to take supplements containing 150 $μ$g iodine/day preconception, during pregnancy, and during lactation.