According to a new study most brands of multivitamins for pregnant women do not contain as much iodine as stated on the label and as iodine is important for a developing fetus it can put babies at risk of poor brain development.

The researchers in a letter in the Feb. 26 issue of the New England Journal of Medicine noted that the levels of iodine that were found in the supplements were below the dosage recommended by the American Thyroid Association (ATA).

Dr. Elizabeth Pearce, co-author of the letter and an assistant professor of medicine at Boston University Medical Center said, "Iodine nutrition is critically important in pregnancy. Women who are deficient in pregnancy have children often with lower IQs or neurocognitive delays. Iodine deficiency is the leading cause of preventable mental retardation in the world."

On the basis of the new findings, "it seems that an ideal prenatal vitamin, in terms of iodine, does not exist," she said. "About half of them have iodine that's derived from kelp and that's very variable."

The study by scientists at the Boston University Iodine Research Laboratory found many of the 60 brands they tested to fall short of the iodine that was stated on the label and what was actually found. They also found the "natural" vitamins that get their iodine from kelp rather than a salt form were found to be more at risk of too little iodine.

The researchers found 127 nonprescription and 96 prescription prenatal vitamins currently available in the United States from an Internet search. 114 products (87 nonprescription and 27 prescription) had claimed iodine was present while the labels of 101 (89%) of these products said they contained at least 150 micrograms of iodine in a daily dose. Sixty-seven vitamins contained iodine from potassium iodide, 42 from kelp, and five from some other source.

In vitamins with potassium iodine the average iodine level was 119 micrograms per daily dose - less than the recommended amount. Among kelp-containing vitamins, the iodine levels ranged from 33 to 610 micrograms per daily dose. In 10 brands, iodine levels were less than half than what was listed on their labels while three brands contained iodine levels 50 % or more than advertised. Kelp-containing vitamins had greater variations.

"Products containing iodine from potassium iodide tended to be more consistent, [but] 150 micrograms of potassium iodide is not the same as 150 micrograms of iodine," said Pearce. "If you really want people to get what the American Thyroid Association [ATA] has recommended -- which is 150 micrograms [of iodine] a day in a supplement -- there isn't one, but we would prefer products made from potassium iodide."

Iodine deficiency is the leading cause of mental retardation and affects more than 2 billion people worldwide. It is commonly added to table salt and can be found in seafood, dairy products and bread. According to the Institute of Medicine and the World Health Organization the requirements for pregnant and nursing women are 220 to
290 micrograms of iodine a day while the American Thyroid Association recommends that pregnant women require a daily dose of prenatal multivitamins containing 150 micrograms of iodine.

Pearce said that based on the study's findings pregnant women should take prenatal supplements that contain potassium iodine rather than kelp.