ABSTRACT
Pregnancy is recognized as an independent risk factor for venous thromboembolism leading
to thromboembolic events, particularly in women with prior venous thrombosis, family
history of thrombosis, or additional thrombophilic risk factors. To reduce the incidence
of venous thromboembolism in pregnancy and improve outcomes, an individual risk stratification
on the basis of probability of thrombosis as a rationale for an individual risk-adapted
prophylaxis is required. In women without prior thrombosis, the presence of a heterozygous
factor V Leiden or heterozygous G20210A mutation in the prothrombin gene is associated
with a pregnancy-associated thrombotic risk of approximately 1 in 400. Thus, in pregnant
carriers of either one of these mutations the risk of venous thromboembolism is low.
For this reason, routine thrombophilia screening of all pregnant women is not recommended.
However, a combination of the two genetic risk factors can increase the risk to a
modest level (risk 1 in 25). In women with a single episode of prior thrombosis associated
with a transient risk factor (such as surgery or trauma) and no additional genetic
risk factor, the probability of a pregnancy-associated thrombosis also appears to
be low. In contrast, in women with a prior idiopathic venous thrombosis who carry
an additional hereditary risk factor or who have a positive family history of thrombosis,
a high risk (> 10%) can be expected, supporting the indication for active antepartum
and postpartum heparin prophylaxis. In many cases, the absolute magnitude of risk
is unknown or estimated, and recommendations are often empiric.
KEYWORDS
Pregnancy - venous thrombosis - risk factors - therapy - prevention
