Iodine nutrition of pregnant and lactating women in Hong Kong, where intake is of borderline sufficiency

Objective: To describe the iodine nutrition of pregnant and lactating women in Hong Kong, where intake is of borderline sufficiency. Design: Review of cross-sectional and prospective studies. Setting: China, Hong Kong Special Administrative Region (SAR). Subjects: Pregnant and lactating women. Results: Studies of pregnant women in Hong Kong SAR have revealed an increase in the urinary iodine (UI) concentration as pregnancy advances. A significant percentage of women had a sub-normal serum thyroid hormone concentration at full term. Although iodine is concentrated by the mammary gland, 19% of all mothers had low iodine concentrations in their breast milk. The moderate correlation between the concentrations of iodine in breast milk and urine suggests that an adequate maternal urinary iodine concentration cannot reliably indicate that an infant is getting enough iodine in breast milk. Therefore, some breast-fed infants may still be at risk of low iodine intake, and additional iodine supplements, other than salt iodisation, would be warranted in this population. Conclusions: The currently recommended intake of iodine through universal salt iodisation may not be adequate for pregnant and lactating women, and supplementation during pregnancy and lactation should be further considered in light of the latest recommendations.