Iodine status in pregnant women in Norway

Background: Iodine deficiency is one of the most widespread nutritional disorders worldwide and has multiple adverse effects on growth and development in humans. Inadequate iodine intake during pregnancy may lead to irreversible foetal brain damage. \n\nObjective: The overall objective of this study was to assess iodine status in pregnant women in Oslo and Akershus by evaluating urinary iodine concentration (UIC), urinary iodine excretion (UIE), and iodine intake from food and supplements.\n\nMethods: A cross-sectional study was performed during 2016 by convenient sampling in 804 pregnant women (18-44 years) in eight Mother and Health Centres in Oslo and Akershus. Spot urine samples were collected from 728 women for assessment of UIC and 804 participants provided information about 24-h iodine intake and supplement use. In addition, 49 participants in a sub-study collected a 24-hour urine sample for assessment of UIC and UIE, and answered a 24-hour dietary recall and a food frequency questionnaire comprising 31 food items. \n\nResults: The median UIC was 92 μg/L (n=777), which according to WHO reflects insufficient iodine intake. The median UIE was 120 μg/24h (n=49). In the large study, median 24-hour iodine intake from food and total iodine intake was 110 μg/day and 148 μg/day. In 24-hour recall, the median iodine intake from food and total intake was 114 μg/day and 143 μg/day. The median habitual iodine intake from food and total was 117 μg/day and 149 μg/day. Milk/dairy was the main dietary iodine source (contributing ~50%), followed by seafood (contributing 25%). The median iodine intake estimated from UIC and UIE was 157 μg/day and 133 μg/day (n=49). The predictors for UIC were smoking, low metabolism, maternal age, and iodine from supplements. Together they explain 11% of the variance in UIC. \n\nConclusions: The findings from the present study indicate suboptimal iodine status due to insufficient iodine intake in pregnant women in Norway, shown through UIC and estimated iodine intake.