Iodine deficiency in pregnant women living in the South East of the UK: the influence of diet and nutritional supplements on iodine status

Abstract

Iodine is a key component of the thyroid hormones which are crucial for brain development. Adequate intake of iodine in pregnancy is important as in utero deficiency may have lifelong consequences for the offspring. Data on the iodine status of UK pregnant women are sparse, and there are no such data for pregnant women in the South East of the UK. A total of 100 pregnant women were recruited to a cross-sectional study carried out at the Royal Surrey County Hospital, Guildford, at their first-trimester visit for an ultrasound scan. The participants provided a spot-urine sample (for the measurement of urinary iodine concentration (UIC) and creatinine concentration) and 24 h iodine excretion was estimated from the urinary iodine:creatinine ratio. Women completed a general questionnaire and a FFQ. The median UIC (85·3 μg/l) indicated that the group was iodine deficient by World Health Organisation criteria. The median values of the iodine:creatinine ratio (122·9 μg/g) and of the estimated 24 h iodine excretion (151·2 μg/d) were also suggestive of iodine deficiency. UIC was significantly higher in women taking an iodine-containing prenatal supplement (n 42) than in those not taking such a supplement (P< 0·001). In the adjusted analyses, milk intake, maternal age and iodine-containing prenatal supplement use were positively associated with the estimated 24 h urinary iodine excretion. Our finding of iodine deficiency in these women gives cause for concern. We suggest that women of childbearing age and pregnant women should be given advice on how to improve their iodine status through dietary means. A national survey of iodine status in UK pregnant women is required.

Figures

Figure 1

Iodine status of women by use of iodine-containing supplements. UIC significantly higher in women taking an iodine-containing supplement (P<0·0001) than in non-users (analysis on log-transformed data).

Figure 2

Adjusted geometric means (95% CI) of estimated 24-hr iodine excretion (computed by back-transformation of the log-transformed 24-hr iodine excretion) by maternal milk intake [variables included in the model: frequency of egg intake, maternal age (yrs), use of iodine-containing supplement, tertiles of weekly seafood intake (g)]. Dashed line represents the expected value (225 μg) in a 24-hr iodine excretion if 250 μg iodine (the dietary requirement for pregnant women) were consumed/day of which 90% was excreted.