COLUMBUS, Ohio (WCMH) -- With marijuana becoming more accessible around the nation, researchers at Nationwide Children's Hospital wanted to know how its usage by pregnant women could affect children's development. Sarah Keim, principal investigator with the Abigail Wexner Research Institute, said the study involved around 250 pregnant women. Each woman shared information with researchers, including details about their lifestyle and behavior.   The study looked at the same pregnant women's children after they had given birth. When each participant's child reached the age of five, they were evaluated.   Mr. Tree replica to be on display at Columbus Metropolitan Library Researchers conducting the study found the children who were exposed to marijuana prenatally had greater difficulties paying attention, planning and controlling their impulses, and they exhibited more aggressive behavior. Keim said research like this is critical with the changing landscape of marijuana use and availability.   “Evidence based on what might be the harm on that to children was really rather old – some of those studies were from the '70s and '80s,” Keim said. “Today marijuana is a lot more potent than it was back then, and our population is a lot more diverse than it used to be.” Keim said researchers will continue the study and check in with those same families when their children reach age seven to see how they are progressing. She said the team also plans to conduct interviews with the students' teachers to gain insight into their development in a classroom setting, both socially and academically.