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Women are hypercoagulable for the first 6 weeks postpartum, but the time course of thrombotic risk thereafter is unclear. To assess extended postpartum clot risk, researchers analyzed hospital discharge claims data from all California women who delivered between 2005 and 2010.
In models adjusted for factors such as age, race, smoking, and predisposition to clot, incidence of a first thrombotic event (ischemic stroke, acute myocardial infarction, or venous thrombosis) 7 to 12 weeks after delivery was twice that at 1 year postpartum, for an absolute risk difference of 3.0 thrombotic events per 100,000 deliveries. Thrombotic risk leveled off after 12 weeks postpartum.
Kamel H et al. Risk of a thrombotic event after the 6-week postpartum period. N Engl J Med 2014 Feb 13; [e-pub ahead of print] (http://dx.doi.org/10.1056/NEJMoa1311485)
Comment
Although we need further study of postpartum clot risk, I will now consider offering thrombotic prophylaxis to high-risk women throughout the first 12 weeks after delivery. In addition, although the CDC has stated that women without risk factors for thromboembolism can generally initiate estrogen-containing contraception 21 to 42 days after delivering (while women with cesarean deliveries or previous thrombosis should wait 42 days postpartum [NEJM JW Womens Health Jul 28 2011]), I will encourage my postpartum patients to wait 12 weeks before using estrogen-containing contraception. For those who want immediate postpartum contraception, intrauterine devices and implants offer highly effective reversible contraception without increasing clot risk.