Even women who have a normal pregnancy run the risk of getting a blood clot. A clot is a clump of blood that has changed from a liquid state to a solid state. They can form while you are pregnant or following delivery.

All pregnant women experience changes in their bodies during a pregnancy, both inside and out. One such change occurs in the blood. The blood increases its tendency to coagulate (form clots) as a safeguard to prevent a miscarriage or a hemorrhage during delivery. But this can lead to the formation of venous blood clots in the leg and pelvic region — a condition called deep vein thrombosis (DVT).

When a blood clot forms inside a blood vessel like an artery or a vein, it can be dangerous. This is because the clot can break off and travel through the blood into an artery in the lungs, heart, brain, or other organs and block the flow of blood. It can also cause a miscarriage, stillbirth, or other pregnancy complication. Blood clots can be fatal.

If a woman has any other conditions that can lead to an even greater tendency to form blood clots, she may want to consider having anticoagulation therapy during pregnancy.

In this type of therapy, medications are used during the course of a pregnancy to help thin out the blood and prevent clots from forming.

What Increases the Risk for Blood Clots During Pregnancy?

Blood clots during pregnancy are rare. According to the American Pregnancy Association, they affect only one or two out of every 1,000 pregnant women.

Some diseases and disorders can increase the chances of having blood clots during pregnancy. These include the following:

  • hereditary blood clotting disorders
  • cancer
  • inflammatory bowel disease, including Crohn’s disease and ulcerative colitis
  • heart disease or heart failure
  • having an artificial heart valve
  • high blood pressure
  • dehydration
  • pre-existing diabetes
  • recent surgeries, especially joint replacements
  • family history of blood clots
  • prolonged immobility
  • smoking
  • being overweight
  • expecting multiples
  • giving birth via cesarean delivery
  • increased maternal age (over age 35)

The increased risk for blood clots can continue for six weeks after you deliver.

What Is Anticoagulation Therapy?

Medications are used to treat and prevent blood clots from forming in high-risk pregnant women. These drugs are called anticoagulants, but are sometimes called blood thinners. They decrease your blood’s ability to clot. They keep existing clots as small as possible while decreasing the chance that you’ll develop more clots.

Usually you will first receive an injection (shot) of a blood thinner called heparin (or low molecular weight heparin (LMWH)) for a few days. Your treatment may then be followed by another injectable type of blood thinner or a blood thinner available in pill form called warfarin (Coumadin). Warfarin is typically only used after giving birth since it can have negative effects on the fetus.

It is important that you take your medication exactly as prescribed. If you take too much or too little, it can be dangerous. Treatment usually lasts for a total of three to six months.

It is also important to stay physically active during your pregnancy. Immobility is a major factor that can lead to blood clots in the legs.

Walk around regularly if you sit for long hours at a desk or travel frequently. Speak with a doctor to see which activities and exercises you can do safely while pregnant. You might also need to see a hematologist, a doctor who specializes in treating conditions of the blood.