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A new study has linked mild iodine deficiency in the womb to lower scores on literacy tests.

Researchers found that 9-year-old who did not receive enough iodine in the womb performed worse on literacy tests, according to the study published in the Journal of Clinical Endocrinology & Metabolism (JCEM).

Iodine is a chemical element the body needs but cannot produce. It plays an essential role in brain development and metabolism, and new research suggests that even mild deficiency during pregnancy can harm the baby's neurological development

"Our research found children may continue to experience the effects of insufficient iodine for years after birth," lead researcher Kristen L. Hynes, PhD, of the Menzies Research Institute at the University of Tasmania in Australia, said in a news release.

"Although the participants' diet was fortified with iodine during childhood, later supplementation was not enough to reverse the impact of the deficiency during the mother's pregnancy," she added.

The latest longitudinal study involved 228 children whose mothers attended the Royal Hobart Hospital's antenatal clinics in Tasmania between 1999 and 2001. Researchers compared the children's standardized test scores and found that those during a period of mild iodine deficiency in the population scored lower on literacy tests, particularly in spelling.  Researchers explained that the conditions were reversed when bread manufacturers began using iodized salt in October 2011 as part of a voluntary iodine fortification program.

However, researchers found that inadequate iodine exposure was not associated with lower scores on math tests. Hynes and her team say the findings suggest that iodine deficiency may take more of a toll on the development of auditory pathways and consequently auditor working memory.  Therefore, iodine deficiency would affect students' spelling ability more than their mathematical reasoning ability.

"Fortunately, iodine deficiency during pregnancy and the resulting neurological impact is preventable," Hynes added.

"Pregnant women should follow public health guidelines and take daily dietary supplements containing iodine. Public health supplementation programs also can play a key role in monitoring how much iodine the population is receiving and acting to ensure at-risk groups receive enough iodine in the diet," she concluded.