It wasn't so long ago that psychologists theorized that autism was caused by mothers who were unable to show affection toward their children. It's hard to believe, but these moms were actually referred to as "refrigerator mothers." Huge strides have been made in terms of understanding that autism is not a result of something a parent does to a child. The condition remains heartbreaking, however.

These days the term "autism" is applied to a range of brain disorders characterized by poor communication and interaction with others. According to the most current statistics from the Centers for Disease Control and Prevention, autism now affects one out of every 110 American children between ages three and eight. (That is when the condition is typically diagnosed.) And while experts still don't know for sure what the cause is, researchers are making some impressive strides toward solving the mystery.

Irva Hertz-Picciotto, PhD, MPH, a professor at the School of Medicine at the University of California in Davis (UC Davis), is one of the authors of two recent studies on autism, both reported in Epidemiology. One study shows that children conceived during winter months (December through March) have an increased chance of being autistic. The other shows that women who take prenatal vitamin supplements in the three months prior to conception and the first month after conception are less likely to bear autistic children.

"The studies present us with more evidence that autism isn't caused by a single factor," Dr. Hertz-Picciotto said. In fact, she said there's mounting evidence that autism is caused by a combination of genetic and environmental factors...which aren't necessarily the same in each case.

In one of the studies, researchers at UC Davis looked at approximately 6.6 million birth records in California filed from 1990 through 2002, correlating the rates of autism for children conceived in December through March with those conceived in July.

The results were surprising: Children conceived in December had an 8% greater chance of being autistic than those conceived in July.

The results were surprising: Children conceived in December had an 8% greater chance of being autistic than those conceived in July…and the percentage of increase over the July rate kept rising for subsequent winter months, reaching a high of 16% in March.

"We don't believe the calendar month itself is a cause of autism, but it's a marker for other potential causes that may vary with the season," said Dr. Hertz-Picciotto, who is also affiliated with the UC Davis MIND Institute, a research center for the study of autism and other neurodevelopmental disorders. She said these other seasonal factors may include viruses that are more common in winter months or the change in the amount of daylight, which affects, among other things, the body's production of vitamin D.

Vitamins May Have A Critical Role

In the second study, researchers collected data from some 700 California families who had children with autism. Results of the study, Dr. Hertz-Picciotto said, showed a reduction of about 40% in autism rates in cases in which the mother had taken prenatal vitamin supplements during the three months before conception through the first month after conception. In other words, a buildup of vitamins before the crucial first month of embryonic development seems to be key to healthy neural growth. Prenatal supplements typically contain vitamin A, niacin (vitamin B-3), folic acid (vitamin B-9), vitamin B-12, vitamin C, vitamin D, vitamin E calcium, iron, pyridoxine, riboflavin, thiamine and zinc.

Folic acid may be the critical component, said Dr. Hertz-Picciotto, because the vitamin is known to protect against defects in the embryo's neural tube, which develops into the brain and spinal cord. With so many factors still unknown, Dr. Hertz-Picciotto said, more studies are expected to be conducted in the near future, especially research into B and D vitamins as well as fevers, infections and exposure to pesticides during pregnancy.

In the meantime, given the vitamin study's finding of a 40% reduction in autism rates, it's certainly wise to take prenatal vitamin supplements three months before potential conception through the first month after conception.

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