The thrombophilias are a group of disorders that promote blood clotting. 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 Venous thrombosis or certain pregnancy complications. 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. Pulmonary embolus is the leading cause of maternal death in the United States.
The thrombophilias also may contribute to pregnancy complications including:Fetal loss. This may occur late in the first trimester (miscarriage) or in the second or third trimesters (stillbirth). and Placental abruption. In this condition, the placenta peels away from the uterine wall, partially or completely, before delivery. .Some pregnant women with a thrombophilia are treated with low moecular weight heparins, such as Lovenox. 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.
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. 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.
While MTHFR heterozygosity itself does not increse risk of thrombosis or fetal compications, when combined with the prothrombin mutation, the risk incrases exponentially.
- Lockwood, C.J. and Bauer, K.A. Inherited Thrombophilias in Pregnancy. UpToDate, April, 13, 2006.
- Lockwood, C.J. Preventing VTE: Part 3—The Pregnant Patient. Contemporary Ob/Gyn, May 2005, pages 11-12.
- James, A.H., et al. Thrombosis During Pregnancy and the Postpartum Period. American Journal of Obstetrics and Gynecology, volume 193, number 1, July 2005, pages 216-219.
- American College of Obstetricians and Gynecologists (ACOG). Thromboembolism in Pregnancy. ACOG Practice Bulletin, number 19, August 2000.
- American College of Obstetricians and Gynecologists (ACOG). Antiphospholipid Syndrome. ACOG Practice Bulletin, number 68, November 2005.