Sickle Cell Trait and the Risk of Venous Thromboembolism

The purpose of this trial is to investigate D-Dimer levels, a surrogate marker of venous thromboembolism, in pregnant/postpartum white women as compared to pregnant/postpartum black women, and pregnant/postpartum women with sickle cell trait. The investigators will determine whether increased D-Dimer levels are reflected in a greater incidence of thrombosis in the postpartum patient, as well as the prevalence of symptomatic venous thrombosis in black patients as compared to pregnant white patients and women with sickle cell trait. The investigators will also investigate the effect of blood group on these parameters. If there is evidence that there is an increased risk of thrombosis in sickle cell trait, the investigators will plan a trial of prophylactic anticoagulation during the last trimester and the four weeks post partum for patients with sickle cell trait and compare this population to patients who do not receive prophylactic anticoagulation.