Pregnancy and the increased risk of developing blood clots
The three main risk factors that increase the risk of developing deep vein thrombosis and/or pulmonary embolism are abnormal clotting, reduced blood flow, and damage to the veins. These risks are all higher during pregnancy, most likely because of:
- Changes in hormone levels and blood composition that influence clotting.
- Reduced blood flow in the legs due to the weight of the fetus pressing upon veins.
- Injury to veins during delivery or surgery.
- Inactivity after cesarean section surgery or delivery.
Women who are obese, are older than 35, or have a family or personal history of blood clots have a higher risk of developing a clot that can lead to pulmonary embolism.
Soon after giving birth, the risk of developing deep vein thrombosis or pulmonary embolism rises by 5 times.1 If a woman has a cesarean section, she is even more likely to develop one or more of these clots.2 This risk usually returns to normal after a few weeks after delivery.
Women with the following history may be screened for genetic factors that can increase the risk of forming blood clots:
- A personal or family history of deep vein thrombosis or pulmonary embolism
- Repeated miscarriages, especially during the second trimester
- Stillbirth
- Severe or recurrent low birth weight (intrauterine growth restriction)
- Preeclampsia
For pregnant women who are more likely to develop blood clots, several methods may be used to prevent deep vein thrombosis and pulmonary embolism. These include:
- Wearing compression stockings.
- Taking unfractionated heparin (UH) or low-molecular-weight heparin (LMWH).
For pregnant women who are diagnosed with deep vein thrombosis or pulmonary embolism, treatments may include:
- Heparin (an anticoagulant medication). Unfractionated heparin or low-molecular-weight heparin is used because neither has been shown to affect the fetus.
- Warfarin (another type of anticoagulant). This medication can be used after delivery. Warfarin may cause miscarriage or birth defects if used during pregnancy, especially in the first 6 to 9 weeks. There is also an increased risk of bleeding in the fetus and the mother, particularly during the third trimester.
If a woman has deep vein thrombosis during or after pregnancy, anticoagulant medication is usually continued for 6 weeks to 3 months after giving birth.3
| Author: | Robin Parks, MS | Last Updated: January 15, 2008 |
| Medical Review: | E. Gregory Thompson, MD - Internal Medicine Jeffrey J. Gilbertson, MD - Cardiovascular Surgery | |
 | ||