METHODS
Using claims data on all discharges from nonfederal emergency departments and acute care hospitals in California, we identified women who were hospitalized for labor and delivery between January 1, 2005, and June 30, 2010. We used validated diagnosis codes to identify a composite primary outcome of ischemic stroke, acute
myocardial infarction, o venous thromboembolism. We then used conditional logistic regression to assess each patient's likelihood of a first thrombotic sequential 6-week periods after delivery, as compared with the corresponding 6-week period 1 year later.