Objective: To examine the use of the modified Wells score in pregnancy as a risk stratification tool in the diagnosis of pulmonary embolism (PE).

Methods: All pregnant or post-partum patients who were referred for CT Pulmonary Angiography (CTPA) to evaluate suspected PE over a 5 year period were included in the study. Patient records were used to apply the MWS and analyze their risk of PE.

Results: A total of 125 women were referred for CTPA over 5 years. A MWS of 6 or greater ("High Risk") was 100% sensitive and 90% specific with a positive predictive value of 36% for PE on CTPA. No patients with a low MWS (less than 6) had a PE, giving a negative predictive value of 100%. P=<0.001. D-dimers, chest X-ray, blood gases and EKG were significantly less effective than the MWS in aiding the diagnosis of PE.

Conclusion: Current methods employed for the diagnosis of PE are inadequate. Risk stratification using the MWS may allow safe exclusion of PE before resorting to CTPA. To the best of our knowledge this is the first study to have used the MWS in a pregnant patient group.