Urinary and Breast Milk Iodine Concentrations in Lactating Mothers and its Association with Certain Demographic Characteristics in an Area with Iodine Sufficiency

Lactating mothers and breastfed infants are most vulnerable to iodine deficiency. The aim of this study was to assess the iodine status of lactating mothers and its association with certain demographic characteristics in an area of iodine sufficiency. In this cross-sectional study, 264 lactating mothers, 3–5 days postpartum were randomly selected from health care centers. Breast milk, urine, and salt samples were collected from each mother. Demographic factors including age, education, occupation, date of last pregnancy, parity, gravidity, type of delivery and use of iodine containing supplement during pregnancy were assessed. A total of 254 lactating mothers, aged 28.2±4.9 years completed this study. Median (interquartile range [IQR]) maternal urinary iodine concentration (UIC) and breast milk iodine concentration (BMIC) was 82 (42-146) and 241 (167-337) µg/L, respectively. Significant correlations were observed between maternal UIC and BMIC (r =0.177, P=0.007). In multiple linear regression, maternal UIC value was associated with occupation (P=0.010) and parity (P=0.014); a significant association was observed between BMIC and occupation (P=0.039) and the iodine content of salt (P=0.043). The present findings indicate that despite lactating mothers being mildly iodine deficient, as defined by median UIC, the iodine levels of breast milk were within an optimal range. In an area with iodine sufficiency, parity, occupation and iodine content of salt are major determinants of iodine status among lactating mothers.