D-dimer testing has an important role in the exclusion of acute venous thromboembolism (VTE) in the nonpregnant population. Establishing D-dimers role in the diagnosis of VTE in pregnancy is hampered because of the substantial increase of D-dimer throughout gestational age. In a prospective study we followed 89 healthy pregnant women to establish the reference range of D-dimer for each trimester. D-dimer testing was also performed in 12 women with clinical suspicion of VTE and their results were compared with the established new reference range of D-dimer, and with the recorded ultrasound findings. In the first trimester, 84% women from reference group had normal D-dimer, in the second 33%, and by the third trimester only 1%, which suggests that D-dimer has no practical diagnostic use in ruling out VTE if the threshold of 230 ng/mL for abnormal is used. All pregnant women with thrombosis who had positive ultrasound findings also had statistically significant elevation of the D-dimer level, considering the established reference range of the corresponding trimester. We found 100% sensitivity of D-dimer test. A women developed thrombosis in the first trimester had 6.7-7.6 time higher level of D-dimer than the mean value in the reference group, and in the third trimester thrombotic women had 2.0-3.8 time higher level of D-dimer, p<0.0001. D-dimer test with the new threshold for: the first of 286, the second of 457 and the third trimester of 644 ng/mL can be useful in diagnosis of pregnancy related VTE.