Urinary Iodine Concentrations Indicate Iodine Deficiency in Pregnant Thai Women but Iodine Sufficiency in Their School-Aged Children

Abstract

The median urinary iodine concentration (UI) in school-aged children is recommended for assessment of iodine nutrition in populations. If the median UI is adequate in school-aged children, it is usually assumed iodine intakes are also adequate in the remaining population, including pregnant women. But iodine requirements sharply increase during pregnancy. In this study, our aim was to measure UI in pairs of pregnant women and their school-aged children from the same family, who were sharing meals, to directly assess whether a household food basket that supplies adequate iodine to school-aged children also meets the needs of pregnant women. UI was measured in spot urine samples from pairs (n = 302) of healthy pregnant mothers and their school-aged children in metropolitan Bangkok, Thailand. A dietary questionnaire was completed. The UI [median (range)] in the pregnant women {108 (11-558) microg/L [0.85 (0.086-4.41) micromol/L]} were lower than those of their school-aged children {200 (25-835) microg/L [1.58 (0.20-6.52) micromol/L]} (P < 0.001), indicating optimal iodine status in the children but mild-to-moderate iodine deficiency in their pregnant mothers. The estimated iodine intakes in the 2 groups were in the range of 130-170 microg/d. There was a modest positive correlation between UI in the pairs (r = 0.253; P < 0.01). A higher frequency of seafood meals was a significant predictor of UI in both groups, but household use of iodized salt was not. These data suggest the median UI in school-aged children should not be used as a surrogate for monitoring iodine status in pregnancy in central Thailand; pregnant women should be directly monitored.

Urinary Iodine Excretion In Pregnancy: A Pilot Study in The Region of Nepal

“…But one of the studies it has been shown that the median UI in school-aged children could not be used as a surrogate for monitoring the iodine status in pregnancy and that pregnant women should be directly monitored [21].…”

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“…Namely, during pregnancy, as a result of physiological changes that occur in a woman's body, the amount of excreted urine increases, and therefore it would be more reasonable to compare ioduria in pregnant women in relation to creatinine excretion. Interesting observations were made by Gowachirapant et al [38], who measured ioduria in school-aged children and their mothers being pregnant at the time of the study; these families lived together and had a similar diet. They noted that ioduria in children was correct; while in pregnant women it indicated a deficiency of iodine in the diet.…”

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“…A recent review concluded that when the median UIC in SAC or non-pregnant women indicated iodine intake was adequate or above requirements in a region, about half the time pregnant women in that same region had inadequate iodine intake (15) . Multiple studies have reported that when SAC have adequate iodine status (median UIC = 100-199 µg/l), pregnant women are deficient (median UIC < 150 µg/l), and that iodine sufficiency in pregnancy is attained only when the SAC have more-than-adequate (median UIC = 200-299 µg/l) iodine status (14,15,(25)(26)(27)(28) . In an earlier Thai study using similar methodology (25) but in families where not all meals were consumed within the household, despite a median UIC of 200 μg/l in SAC, iodine intakes in pregnant women were inadequate, with a median UIC of only 108 μg/l.…”