Dietary iodine inadequate in many pregnant women

OB/GYN News, Nov 15, 2004 by Bruce Jancin

VANCOUVER, B.C. -- More than one-quarter of fetuses may be at risk for neurodevelopmental deficits resulting from exposure to inadequate iodine in American women during pregnancy. Offie P. Soldin, M.D., said at the annual meeting of the American Thyroid Association.

Her analysis of data from the Third National Health and Nutrition Examination Survey (NHANES-III) showed that more than 50% of pregnant women had an iodine intake below the Institute of Medicine's Recommended Daily Allowance of 220 micrograms per day in pregnancy, which corresponds to a urinary iodine level of 150 mcg/L.

Moreover, more than 25% of pregnant U.S. women had a urinary iodine level consistent with an iodine intake less than one-half the RDA, according to Dr. Soldin of Georgetown University in Washington.

Her analysis was based upon 266 pregnant and 3,854 nonpregnant NHANES-III participants aged 15-44 years, all of whom were free of thyroid disease and antithyroid antibodies.

A separate analysis of NHANES-III data by other investigators concluded that 6.9% of pregnant women and 12% of nonpregnant women of childbearing age had a urinary iodine below 50 mcg/L, consistent with outright iodine deficiency, she added.

Adequate intake of iodine in pregnancy is essential for fetal neurologic development. Dr. Soldin attributed the widespread marginal maternal iodine intake to a lack of public awareness of this fact coupled with the absence of iodine in most multivitamin supplements.

In a separate presentation, Gregory A. Brent, M.D., noted that Dr. Soldin's NHANES-III findings were mirrored in a report earlier this year by Elizabeth N. Pearce, M.D., and coworkers at Boston University. They measured total urinary iodine concentrations in 100 consecutive healthy pregnant Bostonians and found 49% had values consistent with an iodine intake below the 220-mcg/day RDA in pregnancy. Nine percent had urinary iodine levels below 50 mcg/L (Thyroid 2004;14:327-8).

The American Thyroid Association's Public Health Committee is very interested in encouraging multivitamin manufacturers to increase the iodine content in their supplements. A recent survey showed that only 35% of prescription prenatal vitamins contain iodine. And of those that do, a mere 15% contain more than 150 micrograms of iodine per daily dose.

A daily supplement containing only 150 micrograms may not be sufficient for a pregnant woman with low dietary intake of iodine to achieve the RDA, said Dr. Brent, professor of medicine and physiology at the University of California, Los Angeles.

BY BRUCE JANCIN

Denver Bureau