What is the role of pregnancy in the pathophysiology of thrombophlebitis?

Updated: Aug 31, 2020
  • Author: Padma Chitnavis, MD; Chief Editor: Dirk M Elston, MD  more...
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During pregnancy, an increase in most procoagulant factors and a reduction in fibrinolytic activity occur. Plasma fibrinogen levels gradually increase after the third month of pregnancy, to double those of the nonpregnant state. In the second half of pregnancy, levels of factors VII, VIII, IX, and X also increase. [62] Decreased fibrinolytic activity is probably related to a decrease in the level of circulating plasminogen activator. [63] In addition, a 68% reduction in protein S levels is measured during pregnancy and in the postpartum period. [64] Protein S levels do not return to the reference range until 12 weeks after delivery. These changes are necessary to prevent hemorrhage during placental separation.

The hypercoagulable condition of the immediate antepartum period is responsible, in large part, for the development of superficial thrombophlebitis and DVT in 0.15% and 0.04% of this patient population, respectively. [65] Even more important is the immediate postpartum period, during which the incidences of superficial thrombophlebitis and DVT increase to 1.18% and 0.15%, respectively. A Dutch study of pregnant women with age-matched controls found a 5-fold increased risk of venous thrombosis during pregnancy. This increased to 60-fold during the first 3 months after delivery. [66] Fifty-percent of DVT cases develop by the second day after delivery, and 84% of DVTs in pregnancy occur in the left leg. [67]

Because normalization of most coagulation factors generally occurs by postpartum day 3, [68] additional factors are suspected in the 21% of patients in whom a DVT subsequently develops 2-3 weeks after delivery. Maternal age may also be linked to venous thrombosis, although study results are conflicting; one of the studies found the rate is approximately 1 case per 1000 women younger than 25 years, changing to 1 case per 1200 women older than 35 years. [35]

Two thirds of patients in whom postpartum DVT develops have varicose veins. Thus, in addition to the potential adverse effects on the fetus, sclerotherapy should be avoided near term until coagulability returns to normal 6 weeks after delivery.

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