Blood clot (thromboembolic) disorders—deep venous thrombosis (DVT) or pulmonary embolism (PE)—are a leading cause of death in pregnant women.
In thromboembolic disorders, blood clots (thrombi) form in blood vessels. An embolus is a blood clot that travels through the bloodstream and blocks an artery.
The risk of developing a thromboembolic disorder is higher in pregnant than nonpregnant people and continues to be increased for about 6 weeks after delivery. Cesarean delivery, like other surgeries, also increases risk.
Symptoms may be similar to those in people who are not pregnant. Thromboembolic disorders can occur without symptoms, with only minimal symptoms, or with significant symptoms.
A clot in the deep veins (deep vein thrombosis) causes symptoms such as calf or thigh swelling, pain, and tenderness. Usually, the symptoms are only in one leg. Foot and ankle swelling is common in pregnancy, but if this is accompanied by other symptoms, a blood clot may be present.
Deep vein thrombosis may also develop in the pelvis. There, it may not cause symptoms. A clot can move from the deep veins of the legs or pelvis to the lungs. There, the clot may block one or more lung (pulmonary) arteries. This blockage, called pulmonary embolism, can be life threatening.
Blood clots can form in the superficial veins of the legs as thrombophlebitis, causing redness or tenderness of the skin and the layers of tissue just below the skin. These types of blood clots are less of a risk and do not travel to the lungs.
Diagnosis of Blood Clot Disorders During Pregnancy
Doppler ultrasound to check for blood clots in the legs
Computed tomography to check for pulmonary embolism
During pregnancy, if women have symptoms suggesting a blood clot, Doppler ultrasound (used to evaluate blood flow) may be done to check the legs for clots.
If pulmonary embolism is suspected, computed tomography (CT) may be done to confirm the diagnosis. CT is done after a radiopaque contrast agent (which can be seen on x-rays) is injected in a vein. The contrast agent flows through blood vessels and outlines them. This procedure is called CT angiography. It is relatively safe during pregnancy.
If the diagnosis of pulmonary embolism is still uncertain, a procedure called pulmonary angiography (angiography of the lung's blood vessels) is required. For this procedure, doctors make a small incision, typically in the groin but sometimes in the arm. Then they insert a thin, flexible tube (catheter) and thread it through blood vessels to an artery in a lung. When the catheter is in place, a radiopaque contrast agent is injected through the catheter to outline the blood vessels in the lungs, and x-rays are taken.
After the baby is delivered, doctors may use CT with a contrast agent to check women for blood clots in the pelvis.
Treatment of Blood Clot Disorders During Pregnancy
Heparin during pregnancy and sometimes after delivery
Warfarin after delivery
If a blood clot is detected, heparin (an anticoagulant, a medication that inhibits blood clotting) is started without delay. Heparin may be injected into a vein (intravenously) or under the skin (subcutaneously). Heparin does not cross the placenta and cannot harm the fetus. Treatment is continued for 3 to 6 months. Then, to prevent new blood clots from forming, doctors give women heparin at a lower dose for at least 6 weeks after delivery. During this time, the risk of blood clots remains high.
After delivery, warfarin may be used instead of heparin, particularly if women require treatment for more than 6 to 8 weeks. Warfarin can be taken by mouth, has a lower risk of complications than heparin, and can be taken by women who are breastfeeding.
Women who have had a blood clot during a previous pregnancy or who had a thromboembolic disorder before they became pregnant may be given heparin during each pregnancy and for 6 weeks after delivery to prevent blood clots from forming.
