Because d-dimer levels increase in pregnancy, it was thought that d-dimer testing is less accurate for diagnosing venous thromboembolism in pregnant women than in nonpregnant women. In this
observational cohort study of 149 pregnant women, a d-dimer assay identified all 13 women with deep venous thrombosis (DVT) (100% sensitivity). However, the small number of women
with DVT means that the d-dimer sensitivity is subject to considerable statistical uncertainty, and the true value could be as low as 70%. Therefore,
in pregnant women with a high pretest probability of DVT, a negative d-dimer test result may not rule out DVT.