Effects of Maternal Iodine Status during Pregnancy and Lactation on Maternal Thyroid Function and Offspring Growth and Development: A Prospective Study Protocol for the Ideal Breast Milk Cohort

Abstract

BackgroundIodine is an intrinsic element of thyroid hormone, which is essential for childhood growth and development. The Ideal Breast Milk (IBM) cohort study aims to evaluate the effects of maternal iodine status during pregnancy and lactation on maternal thyroid function, offspring growth and development, and offspring thyroid function.MethodsThe IBM cohort study recruited pregnant women from Seoul National University Hospital between June 2016 and August 2017, followed by enrollment of their offspring after delivery. For the maternal participants, iodine status is evaluated by urinary iodine concentration (UIC) and dietary records in the third trimester and at 3 to 4 weeks and 12 to 15 months postpartum. For the child participants, cord blood sampling and UIC measurements are performed at birth. At 3 to 4 weeks of age, UIC and breastmilk iodine concentrations are measured. At 12 to 15 months of age, growth and development are assessed and measurements of UIC, a thyroid function test, and ultrasonography are performed.ResultsA total of 198 pregnant women in their third trimester were recruited. Their mean age was 35.1±3.5 years, and 78 (39.4%) of them were pregnant with twins. Thirty-three (16.7%) of them had a previous history of thyroid disease.ConclusionKorea is an iodine-replete area. In particular, lactating women in Korea are commonly exposed to excess iodine due to the traditional practice of consuming brown seaweed soup postpartum. The study of the IBM cohort is expected to contribute to developing guidelines for optimal iodine nutrition in pregnant or lactating women.

Associations between maternal thyroid function in pregnancy and child neurodevelopmental outcomes at 20 months in the Seychelles Child Development Study, Nutrition Cohort 2 (SCDS NC2)

“…al. does indicate that thyroidal changes throughout pregnancy are minimal in iodine sufficient areas, such as Japan and Korea as assessed in these studies, and subsequently the Seychelles as analysed in the present study (40,41) . Thus, it is plausible that the 28-week time point used as a testing point within our Seychellois cohort, who are known to be iodine sufficient, is potentially not dissimilar to thyroid hormone measurements which could be taken at an earlier time point during gestation, e.g.…”

Comparison of Median Urinary Iodine Concentration as an Indicator of Iodine Status among Pregnant and Altered Thyroid Function Women - A Pilot Study

“…Though the upper limits for daily iodine intake is 900 µg/day for adolescent and pregnant women, continuous exposure to high iodine intake may lead to maternal subclinical hypothyroidism. (12) Relatively high prevalence of excessive iodine intake in normal non-pregnant women may be due to consumption of iodine rich foods (milk and dairy products) along with iodized salt which was estimated through 24hr dietary intake and food frequency.…”