Iodine status in pregnancy and household salt iodine content in rural Bangladesh

Adequate maternal iodine intake is essential during pregnancy for the development of the foetus. To assess the extent of iodine insufficiency and its association with household iodized salt in rural Bangladesh, we measured urinary iodine and household salt iodine content among pregnant women in early (≤16 weeks, n=1376) and late (≥32 weeks, n=1114) pregnancy. Salt (~20g) and a spot urine sample (~10mL) were collected from women participating in a randomized, placebo-controlled trial of vitamin A or beta-carotene supplementation in rural northwestern Bangladesh during home visits in early and late pregnancy. Salt iodine was analyzed by iodometric titration, and urinary iodine by the Ohashi method. Almost all salt samples had some detectable iodine, but over 75% contained <15ppm. Median (interquartile range) urinary iodine concentrations were 66 (34-133) and 55 (28-110) μgL^-1 in early and late pregnancy, respectively; urinary iodine <150μgL^-1 was found in ~80% of women at both times in pregnancy. Although the risk of iodine insufficiency declined with increasing iodine content of household salt (P for trend <0.05), median urinary iodine did not reach 150μgL^-1 until iodine in household salt was at least 32ppm and 51ppm during early and late pregnancy, respectively. Despite a national policy on universal salt iodization, salt iodine content remains insufficient to maintain adequate maternal iodine status throughout pregnancy in rural northern Bangladesh. Alternative measures like direct iodine supplementation during pregnancy could be considered to assure adequate iodine status during this high-risk period of life.