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Autism spectrum disorder (ASD) is a group of neurodevelopmental disorders that impact a person’s ability to function socially and results in repetitive behaviors and limited interests. Although the cause of ASD is unknown, research funded by the National Institute of Environmental Health Sciences (NIEHS) has shown that environmental factors play a role. Findings from several recent studies may bring researchers closer to understanding the origins of ASD, a condition that affects approximately 1 in 68 children, according to the .

• A birth study based on 2,734 children, including 102 ASD cases, found that if the mother is both obese before pregnancy and develops diabetes while pregnant, her child has an elevated risk of developing ASD and intellectual disabilities. The study is the first to examine the connection between maternal obesity and diabetes and is a subset of the Boston Birth Cohort.
• Research using semen from fathers of children with ASD suggests that epigenetic differences, or modifications to DNA that do not alter the DNA sequence, may contribute to the risk of having a child with ASD. The samples were obtained from participants in the Early Autism Risk Longitudinal Investigation (EARLI), a study of the prenatal and early life periods of newborns that have biological siblings diagnosed with ASD.
• A study with 45,261 children born at Kaiser Permanente Northern California 2000-2009 confirmed other studies that found second children born less than 2 years or greater than 6 years after the first child, had a 2- to 3-fold increased risk of developing ASD. The increased risk of ASD in second-born children occurred regardless of what happened in the first pregnancy, such as low birth weight, prematurity, cesarean delivery, or having a child with ASD. The scientists caution that more research is needed.