Venous thromboembolism (VTE) occurs infrequently but is a leading cause of illness and death during pregnancy and the puerperium. In the general population the incidence of pregnancy-associated VTE is approximately 1 in 1500 deliveries. The risk of VTE is five times higher in a pregnant than in a nonpregnant woman. Postpartum the VTE risk is even higher. Women with
congenital abnormalities or persistent presence of
antiphospholipid antibodies have an increased risk of VTE during pregnancy and the puerperium. Women with previous VTE have an approximately 3.5-fold increased risk of recurrent VTE during pregnancy.
Heparin does not cross the placenta and is therefore the
anticoagulant of choice. In case of acute
thrombosis during pregnancy, treatment is performed in the same manner as for nonpregnant patients. There is an ongoing debate whether pregnant women with previous
venous thrombosis should routinely receive prophylactic anticoagulation. Patients who have
hereditary antithrombin deficiency,
antiphospholipid antibodies, a combined abnormality, or a history of a severe thrombotic event (
pulmonary embolism or extended
deep vein thrombosis) should be advised to use prophylactic
heparin during pregnancy, starting during the first trimester. Postpartum prophylaxis should be given to all women with an increased risk for VTE. A large body of evidence has been presented that
hypercoagulability may cause
recurrent abortions,
stillbirth, and
preeclampsia. There is no doubt that the
antiphospholipid syndrome is strongly associated with fetal loss. The combination of
heparin and
aspirin significantly decreases the fetal loss rate during pregnancy and thus this is the treatment of choice in this patient group. Several studies indicate that women with
recurrent miscarriage may benefit from
heparin administration during pregnancy, however, data from controlled trials have not yet been published. In women with
artificial heart valves, maternal and fetal complications are frequent despite anticoagulation, but oral
anticoagulants can reduce the risk for maternal complications.