Thrombophilias and pregnancy

The thrombophilias are a group of conditions that increase a person’s chances of developing blood clots. People with a thrombophilia tend to form blood clots too easily because their bodies make either too much of certain proteins (called blood clotting factors) or too little of anti-clotting proteins that limit clot formation.

Thrombophilias may pose special risks in pregnancy. Clots are more likely to develop when a person with a thrombophilia has certain risk factors, including being pregnant or in the postpartum period (up to 6 weeks after delivery)

Most women with a tendency to develop blood clots have healthy pregnancies. However, pregnant women with a thrombophilia may be more likely than other pregnant women to develop deep vein clots and certain other pregnancy complications. Even pregnant women without a thrombophilia may be more likely than non-pregnant women to develop deep vein clots and emboli. This is due to normal pregnancy-related changes in blood clotting that limit blood loss during labor and delivery. However, studies suggest that up to 50% of pregnant women who develop a pulmonary embolus (a clot in the lung) or other venous thromboembolism (a clot that breaks off and travels to a vital organ) have an underlying thrombophilia. Pulmonary embolus is one of the leading causes of maternal death in the United States.

Factor V Leiden and prothrombin mutations are the most common inherited thrombophilias and occur in about 5% to 3% of cases, respectively. Antiphospholipid syndrome (APS) is the most common acquired thrombophilia. APS occurs in up to 5% of pregnant women. Aside from possible pulmonary embolus, APS also may contribute to repeat miscarriage, stillbirth, preeclampsia and poor fetal growth.

All pregnant women who have had a blood clot should be offered testing. Your provider also may recommend testing if you have a family history of VTE before age 50. Women who have had three or more miscarriages (before or after 10 weeks of pregnancy) or one pregnancy loss after 10 weeks of pregnancy may be offered testing for APS.

Some women may not need treatment, however women with an inherited thrombophilia who have a history of blood clots are usually treated with an anticoagulant during pregnancy and the postpartum period. It is important for any woman with a clotting disorder to discuss with her health care provider what treatment, if any, is appropriate for her specific case. A family health history of blood clots can make a significant impact on the treatment decision – another good reason to know your family health history.

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