Thrombophilia - A Common Source of Multiple Miscarriages

These Blood Clotting Disorders Are Associated with Pregnancy Loss

Pregnant Asian woman having prenatal checkup
LWA/Larry Williams/Blend Images/Getty Images

Thrombophilia is an increased tendency to form internal blood clots because of a genetic or immune system abnormality. Certain thrombophilias are related to serious pregnancy complications including miscarriage and stillbirth, although the overall risk of these outcomes is small even in women who have thrombophilias.

What Is Thrombophilia?

About 1 in 5 Americans has a thrombophilia, a health condition where the body makes extra blood clots in the blood vessels.

The clots might occur in veins or arteries, posing a risk to the person's health. A person can have a thrombophilia-related disorder with no outward symptoms.

Thrombophilia is associated with miscarriage and later pregnancy loss, because women with these disorders may form small blood clots that cause problems with the placenta or the umbilical cord.

Although women with thrombophilias are at greater risk of pregnancy loss, it's important to note that the overall risk is still small.  Thrombophilias are usually treated in pregnancy with blood thinners. These are sometimes combined with low-dose aspirin.

What Causes Thrombophilias?

Thrombophilias occur when the body makes too much or too little of certain proteins that help make clots. Some thrombophilas are genetic, meaning you inherit them from a parent. Others are acquired, meaning you develop them over the course of your life.

Blood Clots and Pregnancy

The main thrombophilias that cause pregnancy complications are:

  • Antiphospholipid syndrome - an acquired thrombophilia that is a common cause of recurrent miscarriages. This autoimmune disorder is also known as antiphospholipid antibody syndrome or APS, and is similar to lupus.
  • Factor V Leiden - the most common hereditary thrombophilia. Women with this mutation are two to three times more likely to have multiple miscarriages or a second- or third-trimester pregnancy loss.

    Antiphospholipid syndrome is diagnosed in about 10 to 15 percent of women who have recurrent miscarriages. According to the March of Dimes, antiphospholipid syndrome can cause several problems in pregnancy:

    Testing and Treatment for APS

    If you have recurrent miscarriages, it could be caused by a thrombophilia such as APS. Your doctor may test you for APS. This condition can be diagnosed with blood tests that look for the presence of anti-phospholipid autoantibodies (aPL).

    Many people have aPL but not all of them will develop dangerous blood clots or will have miscarriages or other pregnancy complications.

    However, if you have had recurrent miscarriages and your tests show you have aPL, you may be diagnosed with APS and treated with medications during your pregnancy to prevent blood clots.

    The standard treatment for APS in pregnancy is a combination of a blood thinner called heparin and low-dose aspirin. This therapy is safe for you and your developing baby and can help you have a healthy pregnancy.

    Your doctor may also want you to come in for more than the usual number of prenatal appointments so he or she can keep a closer eye on your developing baby's health. Doctors usually use ultrasounds and fetal heart rate monitoring in pregnancies with thrombophilias.


    Thrombophillias. March of Dimes. January 2014.

    Syndrome. American College of Rheumatology. May 2015.

    V Leiden thrombophilia. Genetics Home Reference. Lister Hill National Center for Biomedical Communications. U.S. National Library of Medicine.

    Prima, F.A.F., Valenti, O., Hyseni, E., et al. (2011). Antiphospholipid Syndrome during pregnancy: the state of the art. Journal of Prenatal Medicine.

    Continue Reading