The Thrombophilias and Pregnancy

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http://www.marchofdimes.com/professionals/14332_9264.asp

What are the thrombophilias?The thrombophilias are a group of disorders that promote blood clotting. Individuals with a thrombophilia tend to form blood clots too easily, because their bodies make:
Too much of certain proteins, called blood clotting factors or
Too little of anti-clotting proteins that limit clot formation
Up to 1 in 5 people in the United States has a thrombophilia (1).
What are the symptoms of a thrombophilia?Most people with a thrombophilia have no symptoms. However, some will develop a thrombosis, a blood clot where it does not belong. Often, blood clots form in veins in the lower leg, causing swelling, redness and discomfort. This condition, called deep vein thrombosis, is often diagnosed with ultrasound or other imaging tests. Clots are generally treated with blood-thinning drugs.
Clots can become life-threatening if they break off and travel through the bloodstream to vital organs (called venous thromboembolism or VTE). When the VTE blocks blood vessels in the lungs (called a pulmonary embolus), it can cause serious breathing difficulties and sometimes death. VTEs that block blood vessels in the brain or heart can cause stroke or heart attack.
Clots are more likely to develop when a person with a thrombophilia has other risk factors, including immobilization (due to a bone fracture, for example), surgery, and a family history of VTE in a parent, sibling or child. Pregnancy and the postpartum period (up to six weeks after delivery) are other times of increased risk of VTE in women with a thrombophilia.
What are the risks of a thrombophilia during pregnancy?Most women with a thrombophilia have healthy pregnancies. However, pregnant women with a thrombophilia may be more likely than other pregnant women to develop a VTE or certain pregnancy complications. Some types of thrombophilias pose greater risks in pregnancy than others (1).
Even pregnant women without a thrombophilia may be more likely than non-pregnant women to develop a VTE. 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 80 percent of pregnant women who develop a pulmonary embolus or other VTE have an underlying thrombophilia (1). Pulmonary embolus is the leading cause of maternal death in the United States (2, 3).
The thrombophilias also may contribute to pregnancy complications including (1, 3):
Fetal loss. This may occur late in the first trimester (miscarriage) or in the second or third trimesters (stillbirth).
Placental abruption. In this condition, the placenta peels away from the uterine wall, partially or completely, before delivery. This can cause heavy bleeding that is dangerous for mother and baby.
Doctors believe that these problems may result from blood clots in placental vessels.
What are the most common types of thrombophilias?Most thrombophilias are inherited, though some can develop later in life. Two of the most common thrombophilias are called factor V Leiden and prothrombin mutations (1). These occur in 5 to 9 percent and 2 to 4 percent, respectively, of Caucasians, and are less common in African-Americans and rare in Asians (4). Both are inherited in an autosomal dominant pattern, meaning that an affected person needs to inherit the gene from only one parent. Each child of an affected parent has a 50 percent chance of inheriting the thrombophilia.
Mild hyperhomocysteinemia is another common thrombophilia. This condition is caused by a specific variation (mutation) in a gene called MTHFR. It is inherited in an autosomal recessive pattern. Affected individuals inherit a copy of the abnormal gene from each parent. They also are deficient in folic acid. There are no good estimates on the number of affected individuals in this country.
Some less common thrombophilias include antithrombin deficiency, protein C and protein S deficiencies. Each affects less than 1 percent of people in the United States (4).
Antiphospholipid syndrome (APS) is a thrombophilia that is not inherited, but develops later in life. The frequency of the disorder is not known, though it is more common in women than men (5, 6). In APS, the body appears to mistake certain proteins that attach to fats on the surface of cells as foreign substances and produces antibodies against them. These antibodies may damage blood vessels, leading to blood clots.
APS is considered an autoimmune disorder, like arthritis and systemic lupus erythematosus (SLE). (SLE affects many body systems, though early symptoms may include a facial rash and arthritis.) About one-third of women with SLE have antiphospholipid antibodies in their blood, which may contribute to their increased risk of pregnancy complications (6). While most individuals with APS are otherwise healthy, the disorder is believed to contribute to about 10 percent of repeated fetal deaths (5, 7).
How are the thrombophilias diagnosed?Doctors do blood tests to find out whether or not a person has a thrombophilia.
Which pregnant women should be tested for thrombophilias?All pregnant women who have had a blood clot should be offered testing, according to the American College of Obstetricians and Gynecologists (ACOG) (4). Doctors also may recommend testing if a woman has a family history of VTE before age 50 and/or a history of pregnancy complications, including two or more miscarriages, stillbirth or placental abruption due to undetermined causes (1, 4).
How is a thrombophilia treated during pregnancy?Some pregnant women with a thrombophilia are treated with a blood-thinning drug called heparin (given by injection one or more times daily) or a newer version of the drug called low-molecular weight heparin. These drugs do not cross the placenta and are safe for the baby. Low doses of aspirin also may be recommended along with heparin for some women with APS. Studies show that treatment helps prevent blood clots in the mother and may improve pregnancy outcomes (1, 4).
However, not all women with a thrombophilia need treatment during pregnancy. A woman and her health care provider should discuss her individual risks of blood clots and pregnancy complications and the severity of her thrombophilia before deciding whether or not she needs treatment. Heparin treatment does pose some risk of side effects, including bone loss and potentially dangerous blood changes. The risks appear lower with low-molecular weight heparin.
In general, treatment is not recommended for most pregnant women with one of the less severe thrombophilias (such as factor V Leiden or prothrombin mutations) who have no personal or family history of blood clots or pregnancy complications (1). The risk of VTE is less than 0.5 percent (1 in 200) in pregnant women with factor V Leiden with no personal or strong family history of VTE (2).
Most doctors recommend about six weeks of treatment after birth (when risk of blood clots may be highest) for women with a thrombophilia and a personal or strong family history of blood clots. Women with a known thrombophilia are generally treated with anti-clotting medications after a cesarean delivery.
Heparin or low-molecular weight heparin treatment is recommended throughout pregnancy and the postpartum period for women who have one of the more severe thrombophilias (such as antithrombin deficiency or more than one thrombophilia), even if they have not experienced any blood clots or pregnancy complications (1). Women with a thrombophilia who have a past history of blood clots are usually treated during pregnancy and the postpartum period.
Women with antiphospholipid syndrome are usually treated with heparin and low-dose aspirin (5). Studies suggest that the combination is more effective than either medication alone in preventing pregnancy loss (5).
Women with mild hyperhomocystinemia are usually treated with the B vitamin folic acid. Most doctors don't recommend treatment with heparin or low-molecular weight heparin unless they have a history of VTE or pregnancy complications and the levels of a substance called homocysteine in the blood remain high despite folate therapy (1).
After delivery, women with a thrombophilia may be treated with an oral blood-thinning drug called warfarin, in addition to, or instead of, heparin. Warfarin is considered safe during breastfeeding, but it is not recommended during pregnancy because it can cause birth defects. Doctors usually recommend that women continue treatment with blood-thinning drugs for at least six weeks after delivery (1).