A study published in the August issue of the Annals of Neurology could be a possible breakthrough in narrowing down the causes of autism.

"I think for the first time, we have the possibility of finding an explanation of the problem," said lead author Dr. Gustavo Roman, with the Houston Methodist Neurological Institute said. "But most importantly, we have a way of preventing this from happening."

Dr. Roman and researchers at the Erasmus Medical Centre in the Netherlands studied thousands of pregnant Dutch women and found a lack of iodine in their diets affected fetal brain development.

"The studies showed that when the mothers had very low levels of thyroid hormone early in pregnancy, the chance of having a kid with autism was multiplied by four," explained Dr. Roman explained. "Very seldom do we see these strength of association."

The most common cause of thyroid hormone deficiency is the lack of iodine in the diet.

One in seven Americans is believed to be iodine deficient.

"I think it's very important that women of reproductive age measure the amount of iodine in the urine," Dr. Roman said. "It's a very simple test and if the levels are low, they need to go back to using iodized salt to prevent this from happening."

Along with a thyroid check, Dr. Roman encourages women who are pregnant or who are trying to get pregnant to take prenatal vitamins that contain iodine.

Thyroid hormone deficiency has also been linked to other complications with pregnancy including hemorrhaging, premature labor and high rates of fetal loss.