Abstract
Pregnancy has been widely recognized as a predisposing risk factor for deep vein thrombosis
(DVT). However, it still remains unclear why pregnant women without a history of familial
thrombophilia or antiphospholipid syndrome (APS) have a higher incidence of DVT and
pulmonary embolism (PE) during pregnancy and puerperium. We examined the activated
protein C (APC) system in healthy pregnant women and in patients with the onset of
DVT during puerperium. Sixty unselected Japanese pregnant women without a past or
family history of thrombosis or APS and 3 Japanese women with DVT during puerperium
were evaluated. Endogenous thrombin potential-ratio (ETP-r) was measured by determination
of thrombin-alpha2,-macroglobulin complexes in thromboplastin-activated patient plasma. APC sensitivity
ratio (APC-sr) was calculated by the determination of ETP-r in patient plasma in the
presence and absence of APC (final concentration [conc.] 5.9 nM) to evaluate the functional
APC anticoagulant activity. Mean APC-sr was significantly increased at 30 weeks' gestation
(2.35 ± 0.72) and remained high during puerperium compared with the mean APC-sr in
nonpregnant women (1.15 ± 0.63). Mean APC-sr in patients with DVT at the onset was
significantly higher (3.57 ± 0.54) than mean APC-sr during puerperium was, indicating
that the sensitivity to APC was reduced in the ETP-based assay. These data suggest
a significant reduction in the functional sensitivity to APC associated with an increased
risk of venous thrombosis during pregnancy.
Keywords:
Deep vein thrombosis - pulmonary embolism - activated protein C - endogenous thrombin
potential
