Objective To establish the pregnancy-specific reference range of D-dimer in healthy pregnant women with single pregnancy.

Methods A total of 473 women with routine prenatal care and 68 multiparas were selected for the study. Quantile regression was used to construct the relationship model between the median, fifth and ninety-fifth percentile of D-dimer levels, and pregnancy groups. Mann-Whitney U test was used to compare the relationship between pregnancy stage and 48 h postpartum D-dimer level.

Results Compared with the level of D-dimer in normal population (＜ 2.24 mg/L), the median level of D-dimer in T2 (T2-1, T2-2), T3 (T3-1, T3-2) and postpartum significantly increased (P ＜ 0.05 to P ＜ 0.01). The level of the ninety-fifth percentile D-dimer in different gestational stages was significantly higher than that in normal population (P ＜ 0.01). Three pregnant women were diagnosed as VTE after delivery, all of them were lower extremity venous thromboembolism, and the incidence was 0.55% (3/541). The plasma D-dimer levels in 3 cases were higher than the median level for the corresponding gestation stage.

Conclusions The D-dimer levels continue to increase throughout pregnancy. The use of the newly recommended ninety-fifth percentile cut-off may be beneficial for the diagnosis of VTE in pregnancy.