case ascertainment and detailed clinical information, some outcome events may have represented delayed sequelae of previous thrombotic events.For example, an outpatient in whom venousthromboembolism is diagnosed at 2 weeks after
delivery who is then hospitalized with symptomsof venous thromboembolism 8 weeks later wouldhave incorrectly appeared to have had a firstthrombotic event at 10 weeks after delivery.