Autism spectrum disorder is a developmental disability. People with autism have trouble communicating and with social skills. The U.S. Centers for Disease Control and Prevention says the person also might repeat some behaviors and not want change in their daily activities. Some people with the condition need a lot of help. Others need less.
CDC officials say autism affects one in every 68 children in the United States. More boys than girls are believed to have the condition. But the number of cases appears to be growing. It is unclear whether the growing number shows a real increase or comes from more knowledge about this disorder.
Common signs of autism include trouble making eye contact and a delay in learning how to speak. Some people with severe autism never learn how to talk. Many people with autism also have difficulty understanding facial expressions and the feelings of others. They also have trouble making friends of the same age.
Doctors have learned how to recognize autism, but much is still unknown about its causes.
Researchers at Harvard University have come closer to finding answers. They found that women exposed to the highest levels of fine particulate air pollution late in their pregnancies are two times more likely to give birth to a child with autism. The researchers found that the timing of exposure to pollution was important. They found no increased risk of autism in children whose mothers were around high levels of pollution before becoming pregnant. And the study found air pollution does not seem to increase the risk of children developing autism after they are born.
Marc Weisskopf led the Harvard researchers. He says pregnant women should avoid air pollution as much as possible. But he warns that other things may increase the risk of autism spectrum disorder.
Autism is believed to result from a combination of environmental and genetic factors.
For now, Marc Weisskopf says researchers are trying to identify the exact substances in air pollution that increase the risk of autism.
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