Thrombotic risk during pregnancy: A population study

Objective: To determine the incidence of pregnancy-related venous thromboem bolic events and the relationship to selected risk factors such as maternal age, parity, smoking, preeclampsia, or cesarean delivery. Methods: All Swedish women reported as having pregnancy-related venous thro mboembolic events during 1990-1993 (608 of 479,422 deliveries) were compare d with all thrombosis-free Swedish pregnant women during 1993 (114,940). Results: The incidence of pregnancy-related venous thromboembolic events wa s 13 per 10,000 deliveries. Cesarean delivery was associated with a fivefol d increased risk of venous thromboembolic events. Advanced age was not a si gnificant risk factor itself, but was associated with an age-related increa se in frequency of cesareans. Women with preeclampsia were at a threefold h igher risk postpartum, but at no increased risk before delivery. There was a tobacco consumption-dependent increase in the risk of thrombosis among sm okers. Conclusion: The incidence of pregnancy-related thrombosis was 13 per 10,000 and provided new insights to important risk factors such as age, cesarean delivery, smoking, and preeclampsia. (Obstet Gynecol 1999;94:595-9. (C) 199 9 by The American College of Obstetricians and Gynecologists.).