A new medical study is raising questions about the acetaminophen, the active ingredient in Tylenol and many popular painkillers. Pregnant women have long been told Tylenol, unlike aspirin or ibuprofen, is safe for their developing babies. But in a new study researchers found that children whose moms took Tylenol while pregnant were more likely to develop A.D.H.D. The study didn't find that Tylenol caused A.D.H.D, but it did find a link. Anderson discussed it with Chief Medical Correspondent Dr. Sanjay Gupta.