Pregnancy and the Increased Risk of Developing Blood Clots - Topic Overview
Pregnant women have a higher risk of deep vein thrombosis and pulmonary embolism.1
What raises the risk of blood clots during pregnancy?
The three main risk factors (things that increase risk) for
deep vein thrombosis and
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.
After delivery, the risk for blood clots is higher than during pregnancy. This risk usually returns to
normal after a few weeks after delivery.2
If a woman has a cesarean section, she is even
more likely to develop one or more of these clots.
Who is screened for risk of blood clots?
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
- Severe or
recurrent low birth weight (intrauterine growth restriction)
How are blood clots prevented?
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:
How are blood clots treated?
A pregnant woman who is diagnosed with deep vein
thrombosis or pulmonary embolism will work with her doctor to decide which anticoagulant medicine to take during pregnancy. She may take heparin, because it has not been shown to affect
After delivery, the woman might take another anticoagulant, such as warfarin, for a few weeks or a few months.