Beyond Salt Iodization: Sustained Population Sufficiency and Recurrence of Iodine Deficiency in Pregnant Women in Iran

BACKGROUND: Iodine deficiency disorders (IDDs) remain a public health concern, especially in pregnancy, despite universal salt iodization (USI) programs. Iran has sustained iodine sufficiency since the 1990s through national USI, but recent evidence suggests recurrent iodine insufficiency among pregnant women. This study reports findings from the sixth National Monitoring Survey (2022-2023) to reassess iodine status in schoolchildren and pregnant women in Iran. METHODS: This cross-sectional survey included 11,221 schoolchildren aged 8-10 years and 2929 pregnant women from all 31 provinces. Multistage cluster sampling ensured national representativeness for children. At the same time, pregnant women were recruited from health centers by equal provincial quotas (60 per province, not population-weighted), and their individual intake of iodide along with folic acid supplements was documented. Urinary iodine concentration (UIC) was measured using the Sandell-Kolthoff method, and salt iodine content was assessed by iodometric titration at production and household levels. Data were analyzed with descriptive and nonparametric statistical methods. RESULTS: The median UIC in schoolchildren was 133 µg/L (interquartile range [IQR]: 88-183), within the World Health Organization (WHO)-recommended range, with 67.7% having UIC ≥100 µg/L. However, 22.8% had a UIC of 50-100 µg/L and 9.5%