There might be a connection between pre-term birth and autism, a brain developmental disorder that affects one in 150 U.S. children says a new study. Autism can also impair a child’s ability to communicate and interact with others.

Researchers from Boston University School of Medicine and Boston Medical Center followed 988 U.S. children who were all born at least three months before their due date. Though a formal diagnosis of autism doesn’t occur until around age 3, the children were evaluated at age 2 using a checklist of 23 behaviors that could possibly indicate the disorder. Twenty-one percent of the children scored positive for autism, while only 6 percent of children born full-term screened positive.

While the children born prematurely were about two to three times more likely to show signs of autism at age 2, researchers say that being born before the due date may not directly cause an increased risk for the disorder. In fact, it is possible that whatever causes a child to have autism also may force an early birth.

Learn more about autism here.