Breast milk and infant iodine status during the first 12 weeks of lactation in Tianjin City, China

Abstract

Background and objectives: The present study investigated the iodine status of breast milk and breast-fed infants during the first 12 weeks postpartum in Tianjin, China.

Methods and study design: A total of 175 pregnant women were recruited before delivery. Their breastmilk and 24-h urine samples were collected at 4, 8, and 12 weeks postpartum; spot urine samples were simultaneously collected from their infants. The iodine content of the samples was measured.

Results: The mean breast milk iodine concentrations (BMICs) at 4, 8, and 12 weeks were 221.7±103.5 μg/L, 175.2±76.2 μg/L, and 148.1±66.2 μg/L, respectively. Significant differences existed between the mean BMICs of the three sampling times (F=12.449, p<0.001). The BMIC showed a decreasing trend during the first 12 weeks postpartum. The median urinary iodine concentrations (UICs) of the mothers were 152, 112, and 109 μg/L at the different sampling times. The BMIC and UIC were not correlated in the mothers. The median UICs in the infants were 251, 183, and 164 μg/L. The infant UICs were statistically different at the three sampling times (p=0.001). Moreover, the infant UICs correlated with the BMICs (Rs=0.205, p=0.010) but not with the maternal UICs (Rs=0.131, p=0.067).

Conclusion: The BMIC in and infant iodine intake from breast milk decreased in the first 12 weeks. Breastfed infants could receive adequate iodine from breast milk in Tianjin City.