Pregnancy entails more than morning sickness and fatigue — it also brings a risk of deep vein thrombosis (DVT), a preventable formation of blood clots in the veins. Pregnant women are five times more likely to develop deep vein thrombosis than women who aren't pregnant. The risk continues in the postpartum period — up to three months after the baby is born.About 0.5 - 2.0 of every 1,000 pregnant women experience DVT.DVT is dangerous because an untreated clot can break free and travel through the bloodstream.

"The fear is it will move to the heart or lungs and cause a pulmonary embolism, which can lead to death," says Daniel Roshan, MD, a maternal fetal medicine specialist and an assistant professor of obstetrics and gynecology at the NYU Grossman School of Medicine in New York City.

But you can take steps to prevent blood clots in pregnancy. Here's how to recognize blood clots while pregnant and how to protect yourself from DVT.

Pregnant women have an increased risk of DVT because of the physiological changes that take place during pregnancy, says Pamela Berens, MD, a professor of obstetrics and gynecology with McGovern Medical School at UTHealth in Houston.

One change is the compression in the pelvis from the baby. "There are also changes in clotting factors in the blood that begin early in pregnancy and last until a woman is six weeks postpartum," she adds.

Causes of DVT in pregnancy and the postpartum period include:

• Natural increase in blood clotting, which prepares the body for blood loss during birth

• Slowing of blood flow later in pregnancy from the baby's weight on blood vessels

• Vein injury during delivery

• Long periods of immobility during or after pregnancy

Pregnancy hormones also play a role. "There's a lot of estrogen circulating during pregnancy, and estrogen increases the risk of blood clots," Dr. Roshan says.

Certain factors can further raise your risk of developing DVT in pregnancy or postpartum. For example, women on birth control pills that contain estrogen have an increased risk of DVT, and Roshan says that women with genetic clotting disorders, called thrombophilias, are at an even higher risk.Other DVT risk factors include:

• Age (35 or older)

• Previous blood clot

• Family history of blood clots

• Multiple pregnancy (carrying more than one fetus at one time)

• Surgery or trauma

• Use of estrogen-based hormone therapy

• Being overweight

• Smoking

• Use of fertility treatments involving hormones

• Prolonged immobility, such as bed rest, travel, or recovery after delivery

• Pregnancy-related complications like preeclampsia

• Medical conditions like diabetes

• Cancer and cancer treatment

• Inflammatory bowel disease (IBD)

• Kidney disorders

• Varicose veins

A cesarean delivery (C-section) more than triples a pregnant woman's risk of a dangerous blood clot. Race can also be a risk factor.A review of studies found the overall incidence of DVT and pulmonary embolism is 30 to 100 percent higher in Black Americans than in white Americans.Blood clots can appear anywhere in your body, but most DVTs during pregnancy occur in the legs or pelvic area. "Watch for tenderness in the calf and thighs, pain in the back of your calf, and swelling, particularly if it is on one side more than the other," Roshan says.About half of people with a blood clot have no symptoms at all. But for those who do, symptoms of DVT in your leg, arm, or pelvis can include:

• Swelling (can be sudden)

• Pain while resting, standing, or walking

• Warmth or tenderness to the touch

• Skin redness

• Increased vein size near the skin's surface

Blood clots during pregnancy that move to the heart or lungs can cause chest pain, shortness of breath, cough with blood, lightheadness, or fainting. This signals an even more serious situation. If you feel these symptoms, call your doctor immediately or head to the emergency room.

"If you have any signs of DVT, seek medical attention right away," says Roshan. A healthcare professional can perform an ultrasound of the affected area to see if a pregnancy blood clot is causing your discomfort.

Whether you're at high or low risk for blood clots in pregnancy, it's vitally important to notify your provider immediately if you notice any symptoms.

Even though pregnancy puts you at higher risk for DVT, you can take steps to protect yourself from blood clots. Above all, talk to your provider about your symptoms as much as you need to. When it comes to protecting yourself from DVT, no question is too small.

Be Aware of Your Risk Factors

The more prepared you are, the better you can prevent DVT in pregnancy. Ask the women in your family if they have had blood clots, and notify your provider of any family history or other risk factors.

Keep Moving

Lack of movement can affect your blood flow and increase your risk for DVT in pregnancy, says Dr. Berens. "So stay active and maintain a healthy weight." If you have to be on bed rest because of an injury or complication in your pregnancy, your doctor may prescribe blood thinners as a precautionary measure.

Get Up During Travel

"Flying in itself is a risk factor for DVT, so pregnant women who fly are definitely at an increased risk," Berens says. If you have to fly, get up and move around every hour or two and do ankle roll exercises while you sit. "Do the same thing if you go on a long car or bus ride," she adds.

Wear Compression Socks

Because they improve circulation and reduce swelling in the legs, compression socks can lower your risk of DVT in pregnancy, Roshan says.

Drink Lots of Water

Good hydration during pregnancy helps prevent clots by keeping the blood from getting too thick, Roshan says. Experts recommend that pregnant women drink 8 to 12 glasses of water every day.

Use Prescribed Medication

If you have a DVT, you will probably be treated with a blood thinner like enoxaparin (Lovenox), which is safe during pregnancy. "We treat the clot with a therapeutic dose for a few months and then lower it to a prophylactic (preventive) dose," says Roshan.If your provider prescribes medication for you, it's very important you take it as instructed. If you're not sure how to take it, or have questions about it, let your provider know right away."We usually monitor women taking blood thinners throughout their pregnancies because as the pregnancy progresses, they sometimes need higher doses," Roshan says. "For women with a family history of DVT but no personal past history, we sometimes prescribe baby aspirin and tell them to be particularly cautious about symptoms."

Overall, erring on the side of caution with blood clots can help prevent or catch any potential complications early. "Deep vein thrombosis in pregnancy can be life-threatening, so if you see any signs, don't hesitate to go to your doctor to get checked," Roshan says.

• During pregnancy and up to three months postpartum, your risk for blood clots increases.

• Causes and risk factors of a blood clot, or deep vein thrombosis (DVT), include family and personal history of DVTs, pregnancy, injury, immobility, and being over 35 years old.

• Blood clot symptoms can come on suddenly, typically affect an arm or leg, and can manifest as warmth, tenderness, pain, and swelling in one limb.

• You can prevent DVT in pregnancy by staying aware of risk factors, exercising, wearing compression socks, drinking plenty of water, and using any medications prescribed.

• If you have symptoms of a DVT, let your provider know right away.