To account for all women meeting the study eligibility criteria, this study utilized a combined prospective and retrospective arm. Pregnant women who underwent diagnostic imaging to evaluate for suspected PE at our institution were prospectively enrolled from February 2014 to August 2015. Both d-dimer and BNP serum levels were drawn, and a MWS was assigned. All pregnant women diagnosed with a PE that underwent diagnostic imaging and had a d-dimer level drawn from January 2009 to June 2014 were retrospectively enrolled. Patient electronic records were used to apply the MWS and analyze their risk.