Factor V Leiden: Should All Pregnant Women Be Tested For Clotting Disorders?

One of my friends experienced a stillbirth. It was later discovered, through a simple blood test, that she has a blood clotting disorder (Factor V Leiden and protein C deficiency). If she, or more importantly, her doctors had known of this inherited clotting disorder, she believes her baby would be alive today. Shouldn't there be testing of all pregnant women to prevent tragedies like this from occurring?


Peg Plumbo CNM

Peg Plumbo has been a certified nurse-midwife (CNM) since 1976. She has assisted at over 1,000 births and currently teaches in the... Read more

I am sorry for your friend's loss. Unfortunately, this issue is not so cut and dry. About five percent of Caucasians and one percent of African-Americans have one gene for this mutation and only 0.1 percent have both, which makes them very susceptible to thrombosis.

Pregnancy, oral contraceptive use and estrogen replacement therapy are all risk factors for thrombosis. Pregnancy is a state of "hypercoagulability" in all women. In women who carry the gene for Factor V Leiden and protein C deficiency, this risk increases. Thirty percent of blood clots in pregnancy are caused by the mutation.

Venous thrombosis is caused by a combination of genetic, acquired and environmental influences. Natural anticoagulant systems (the protein C system and antithrombin III) are in place to keep coagulation in check. Excess clotting occurs when there is a disturbance in one of the coagulation inhibitor mechanisms or in natural breakdown of clots.

It is standard practice for women with a history of clots or with the mutation to receive Heparin during pregnancy. Factor V mutation testing should be performed before pregnancy or the prescription of oral contraceptives if there is a personal or family history of thrombosis.

Should we screen everyone? Some believe so; others do not. It is expensive and not everyone who has the mutation would develop thrombosis, so intervention would be done needlessly on many women. There is no agreement on management. Insurance might be denied to those with the mutation. Currently, we screen all women with a personal or family history of thrombosis.

Second trimester pregnancy loss has been associated with the mutation, but we still do not screen those women necessarily. The Centers for Disease Control and Prevention is asking for more research on this topic.

Stillbirth as a result of this mutation is rare. Your friend's baby must have been homozygous (inherited both "bad" genes), or perhaps she experienced a blood clot in labor.

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