Inherited Thrombophilias in Pregnancy

Inherited thrombophilias are associated with an increased risk of venous thromboembolism and also have been linkedto adverse outcomes in pregnancy. However, there is limited evidence to guide screening for and management of theseconditions in pregnancy. The purpose of this document is to review common thrombophilias and their association withmaternal venous thromboembolism risk and adverse pregnancy outcomes, indications for screening to detect theseconditions, and management options in pregnancy.
BackgroundThe Hemostatic Paradox of Pregnancy
Pregnancy poses a particularly complex hemostatic chal-lenge. Successful pregnancy requires the avoidance ofhemorrhage during implantation, endovascular cytotro-phoblast remodeling of maternal spiral arteries, andduring the third stage of labor, yet also requires the main-tenance of a fluid uteroplacental circulation. Maintaininghemostatic balance during pregnancy requires alterationsin both local uterine and systemic clotting, as well asanticoagulant and fibrinolytic proteins. The deciduallayer of the uterus plays a crucial role in the preventionof hemorrhage during implantation, placentation, and thethird stage of labor (1, 2). Confirmation of the crucial rolethat the decidua plays in the maintenance of gestationalhemostasis is seen in the hemorrhage associated withobstetric conditions marked by absent or impaired decidua(eg, ectopic pregnancy and placenta accreta). Conversely,decidual tissue factor also can promote the intense hypofi-brinogenemia and disseminated intravascular coagulationobserved in decidual hemorrhage (ie, placental abruption).
Pregnancy is marked by increased clotting potential,decreased anticoagulant activity, and decreased fibrino-lysis (3–5). The thrombotic potential of pregnancy isexacerbated by venous stasis in the lower extremitiesdue to compression of the inferior vena cava and pel-vic veins by the enlarging uterus, a hormone-mediatedincrease in venous capacitance, insulin resistance, andhyperlipidemia. Thus, it is not surprising that venousthromboembolism complicates approximately 1 in 1,600births and is a leading cause of maternal morbidity in theUnited States (6, 7).
There is a strong association between inherited throm-bophilias and venous thromboembolism, which makesdetection of these mutations a logical target for preventionstrategies (Table 1). However, it is controversial whetherthere is an association between inherited thrombophiliasand uteroplacental thrombosis leading to adverse preg-nancy outcomes such as fetal loss, preeclampsia, fetalgrowth restriction, and placental abruption (8). This pos-sible association has resulted in increased screening forthrombophilias in pregnancy, although there has been noconfirmation of treatment benefits.
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