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

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.