Spontaneous clotting potential in the peripartum maternal circulation

The increased risk for thrombotic events during pregnancy and the peripartum period is well established. Our goal was to analyze the incidence and extent of endogenous clotting potential during the peripartum period that may contribute to the underlying mechanisms.

A prospective longitudinal study enrolled women with uncomplicated pregnancies at 38-41 weeks gestation. Citrated platelet poor plasma was isolated at three visits (one 3rd trimester, and two postpartum). In this secondary retrospective analysis, aliquots were thawed and either centrifuged to remove sedimentable material or not, before being refrozen in advance of subsequent analysis. Exogenously and endogenously initiated coagulation assays were used to assess clot and thrombin formation (Thrombodynamics T2F analyzer and the calibrated automated thrombogram (CAT), respectively). Parameters describing exogenously initiated clot (Clot_TF) and endogenously initiated clot (Clot_Sp) growth, and standard CAT parameters were collected. Comparisons were made across visits and between preparations using paired t-tests. Data are presented as mean ± standard deviation or Spearman correlation values.

Clot_Sp growth was more robust at 18-48 h postpartum compared to the late third trimester. Centrifugation removed all detectable Clot_Sp growth and reduced the speed of Clot_TF growth. In exogenously initiated CAT assays, there were no significant differences across the immediate peripartum period. Depleted preparations had slightly slower dynamics compared to control preparations. We observed a correlation between the rates of Clot_Sp and Clot_TF growth.

Through 18-48 h after delivery there is an increase in endogenous clotting potential compared to late pregnancy, centrifugation of this sedimentable material removes most of this endogenous activity.