In a study prepared by I3 Drug Safety, a service company for the pharmaceutical industry, the authors found that women using the Ortho Evra birth control were more than twice as likely to suffer venous thromboembolisms than woman using oral birth control. There was not sufficient data to assess whether or not there were increased risks of strokes or heart attacks though increased incidence rates were noted. See “Venous Thromboembolism and Myocardial Infarction Among Transdermal Contraceptive Users” J. Alexander Cole, Obstet Gynecol 207; 109:339-46.