Pregnancy factors, parental psychiatric history, and preterm delivery may be associated with the risk of autism

May 23 2005

Pregnancy factors, parental psychiatric history, and preterm delivery may be associated with the risk of autism, according to a recent study supported in part by the Centers for Disease Control and Prevention (CDC). The study, "Risk Factors for Autism: Perinatal Factors, Parental Psychiatric History, and Socioeconomic Status," appears in the most recent issue of the American Journal of Epidemiology.

The research, which involved national study of all 698 Danish children with autism born after 1972 and diagnosed before 2000, focused on perinatal risk factors (i.e., delivery and newborn characteristics, pregnancy characteristics, and parental characteristics), parental psychiatric history (i.e., did a parent have a diagnosed psychiatric illness before the date that autism was diagnosed in the child) and socioeconomic status (i.e., the mom’s formal education and parental wealth at the child’s birth). Previous research had suggested each category may represent or include risk factors for autism.

"This study is a helpful step forward in identifying possible risk factors for autism," said Dr. José Cordero, director of CDC’s National Center on Birth Defects and Developmental Disabilities. "It also indicates there may be some children for whom we need extra vigilance in watching for signs of developmental delay. In recent years, many programs and studies have found that early recognition of autism and other developmental disabilities is important because early treatment can significantly improve a child’s development."

Some of the specific factors that the study found to be associated with the risk of autism included: breech presentation at birth, delivery before 35 weeks, a parent who had a diagnosis of schizophrenia-like psychosis before the date that autism was diagnosed in the child, and low birth weight at delivery. The study also found many of these factors were independently associated with autism. For example, there was an association between adverse pregnancy events and autism, regardless of whether one of the parents had a diagnosed psychiatric illness.

"We need to further investigate the role of events during pregnancy, including their possible interaction with genetic factors, to learn more about potential causes of autism," said Diana Schendel, CDC epidemiologist and one of the authors. "We also need additional research to determine if the factors identified here really play a role in causing autism. Right now, we have only identified possible associations. But if we can find a cause-and-effect relationship, it may help our efforts to prevent autism."

Autism spectrum disorders (ASDs) are a group of developmental disabilities that are caused by unusual brain development. People with ASDs tend to have problems with social and communication skills. Many people with ASDs also have unusual ways of learning, paying attention, or reacting to different sensations. ASDs begin during childhood and last throughout a person's life. CDC funds projects on autism spectrum disorders (ASDs) in several states. These projects track the number of children who have an ASD, conduct studies to find out what factors make it more likely that a child will have an ASD, and offer education and outreach programs for researchers, families, and other people affected by ASD. Large representative studies are needed to answer questions necessary to determine the potential causes of autism and develop prevention strategies for this disorder.