Apparent insufficiency of iodine supplementation in pregnancy

Pregnant woman are at increased risk for iodine deficiency, which may induce thyroid insufficiency and have damaging effects not only on the mother but also the fetus. We hypothesize that iodine supplementation during pregnancy reduces the risk for iodine deficiency.

Cross-sectional study to assess iodine levels in random urine specimens during pregnancy in New York City. One hundred eighty-two women visited a clinic where free iodine supplementation was offered (150 μg of potassium iodide daily; Group A), and 183 women were seen at a practice at which no supplementation was offered (Group B).

Overall, more than one out of two pregnant women in New York City were at risk for iodine deficiency with a spot urinary iodine (UI) level less than 150 μg/L and could be defined as at risk for iodine deficiency. The median urine iodine concentration for the entire group was 152.5 μg/L, but there was considerable variation from 10.9 to 1210 μg/L. The median UI level of the supplemented Group A (169.8 μg/L) was significantly greater than that of Group B (128.4 μg/L; p<0.01). Based on World Health Organization (WHO) guidelines, 38.9% of Group B women were at risk for mild, moderate, or severe iodine deficiency, compared with 22.8% of Group A women.

New York City pregnant women were significantly less prone to iodine deficiency when provided with iodine supplementation. Nevertheless, when spot UI levels were used to estimate iodine sufficiency, more than 20% of supplemented women were still at risk for iodine deficiency according to WHO guidelines, suggesting that current supplementation practices remain insufficient.