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Autism spectrum disorder is a developmental disability. People with autism have trouble communicating and with social skills. They also might repeat some behaviors and not want change in their daily activities. Some people with the condition need a lot of help. U.S. government officials say autism affects one in every 68 children in the United States. But the number of cases appears to be growing. 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. 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 a kind of air pollution are two times more likely to give birth to a child with autism. Marc Weisskopf led the Harvard researchers. They studied women who were in the later part of their pregnancies. In all, they examined medical records from all 50 U.S. states for about 116,000 mothers and their children. The study found that the women who were around high levels of fine particulate matter air pollution were at the highest risk of having an autistic child. They found the risk was only when the mother was pregnant, not before, or after, the child was born. Marc Weisskopf says this finding does not prove there is a direct link between pollution and autism. But, he adds, it has increased his team’s belief that there is a relationship between the two. Autism is believed to result from a combination of environmental and genetic factors.