Resurgence of Iodine Deficiency in the United States During Pregnancy: Potential Implications for Cognitive Development in Children

Iodine is an essential trace mineral for thyroid hormone synthesis, metabolism, and neurological development, particularly during pregnancy and early childhood. Although salt iodization in the 1920s significantly reduced iodine deficiency, recent studies suggest a resurgence in the United States, particularly among pregnant women. This review examines the resurgence of iodine deficiency among women in the United States while highlighting factors influencing intake, focusing on maternal iodine status during pregnancy, followed by its implications on cognitive health of children globally. Articles published from 2010 to 2024 were identified using PubMed, EMBASE, and Cochrane databases following PRISMA 2020 guidelines. Search terms included "iodine deficiency in women" and "maternal iodine deficiency and neurodevelopment." Studies on urinary iodine concentration (UIC) in nonpregnant, pregnant, and lactating women in the United States, and maternal iodine deficiency impact on offspring neurodevelopment globally, were included. Nine articles were reviewed addressing current iodine status among women in the United States, 4 of which used the National Health and Nutrition Examination Survey (NHANES). NHANES data (2011-2020) indicated declining median UIC (mUIC) among women of reproductive age and mUICs in pregnant women were below the World Health Organization recommendation (<150 µg/L). Prevalence of inadequate iodine status ranged from 23% to 59% in pregnant women. The primary contributing factor to declining iodine status is dietary changes, specifically reduced milk consumption. Eleven additional articles examined maternal UIC and cognition in global populations, highlighting the association between low UIC during pregnancy, particularly in the first and second trimesters, and poor neurodevelopmental outcomes such as reduced IQ scores in offspring outside of the United States. Offspring born to mothers with iodine deficiency are at greater risk of poor cognitive health. Comprehensive nutrition policies are needed to raise awareness of adequate iodine intake during critical developmental periods and to support food-system changes, ensuring sufficient intake.