As pregnancy progresses, fluid may accumulate in tissues, usually in the feet, ankles, and legs, causing them to swell and appear puffy. This condition is called edema. Occasionally, the face and hands also swell. Some fluid accumulation during pregnancy is normal, particularly during the 3rd trimester. It is called physiologic edema.

Fluid accumulates during pregnancy because the adrenal glands produce more of the hormones that make the body retain fluids (aldosterone and cortisol). Fluid also accumulates because the enlarging uterus interferes with blood flow from the legs to the heart. As a result, fluid backs up in the veins of the legs and seeps out into the surrounding tissues.

Causes

Common causes: Usually during pregnancy, swelling is

• Physiologic edema

Less common causes: Less commonly, swelling during pregnancy results from a disorder (see Symptoms During Pregnancy: Some Causes and Features of Swelling During Late Pregnancy). However, such disorders are often serious. They include

• Deep vein thrombosis
• Preeclampsia
• Cellulitis

In deep vein thrombosis, blood clots form in veins located deep within part of the body, often in the legs. Pregnancy increases the risk of this disorder in several ways. During pregnancy, the body produces more of the proteins that help blood clot (clotting factors), probably intended to prevent too much bleeding during childbirth. Also, changes during pregnancy cause blood to back up in veins, making clots more likely to form. If the pregnant woman is less mobile, blood is even more likely to back up in leg veins and clot. The clots may interfere with blood flow. If a blood clot breaks loose, it can travel through the bloodstream to the lungs, blocking blood flow there. This blockage (called pulmonary embolism) is life threatening.

In preeclampsia, blood pressure and protein levels in urine increase during pregnancy. Fluids may accumulate, causing swelling in the face, hands, or feet and weight gain. If severe, preeclampsia can damage organs, such as the brain, kidneys, lungs, or liver, and cause problems in the baby.

In cellulitis, bacteria infect the skin and tissues under the skin, sometimes causing swelling with redness and tenderness. Cellulitis most commonly affects the legs but may occur anywhere.

Risk factors: The risk of deep vein thrombosis and preeclampsia is increased by various conditions (risk factors).

For deep vein thrombosis, risk factors include

• A recent leg injury
• A previous episode of deep vein thrombosis
• A disorder that makes blood more likely to clot, such as cancer or sometimes systemic lupus erythematosus (lupus)
• Cigarette smoking
• Immobility, as may occur after an illness or surgery

For preeclampsia, risk factors include

• High blood pressure that was present before pregnancy
• Preeclampsia during a previous pregnancy or a family member who has had preeclampsia
• Age under 17 or over 35
• A first pregnancy
• A pregnancy with more than one fetus
• Diabetes
• A hydatidiform mole (overgrowth of tissue from the placenta)

Evaluation

Doctors must rule out deep vein thrombosis, preeclampsia, cellulitis, and other possible causes before they can diagnose physiologic edema.

Warning signs: In pregnant women with swollen legs, the following symptoms are cause for concern:

• Blood pressure that is 140/90 mm Hg or higher
• Swelling in only one leg or calf, particularly if the area is warm, red, and/or tender or fever is present
• Swelling in the hands
• Swelling that suddenly increases
• Confusion, difficulty breathing, changes in vision, shaking (tremor), a seizure, sudden abdominal pain, or a sudden headache—symptoms that may be caused by preeclampsia

When to see a doctor: Women should go to the hospital immediately if they have

• Symptoms that suggest preeclampsia

Women with other warning signs should see a doctor that day. Women without warning signs should see a doctor, but a delay of several days is usually not harmful.

What the doctor does: Doctors first ask questions about the swelling and other symptoms and about the medical history. Doctors then do a physical examination. What they find during the history and physical examination often suggests a cause of the swelling and the tests that may need to be done (see Symptoms During Pregnancy: Some Causes and Features of Swelling During Late Pregnancy).

Doctors ask when the swelling started, how long it has been present, and whether any activity (such as lying on the left side) lessens or worsens it. Lying on the left side decreases physiologic edema. Doctors also ask about conditions that increase the risk of developing deep vein thrombosis and preeclampsia.

Women are asked about other symptoms, which may suggest a cause. They are asked whether they have ever had deep vein thrombosis, pulmonary embolism, preeclampsia, or high blood pressure.

During the physical examination, doctors look for evidence of a serious cause. To check for symptoms of preeclampsia, doctors measure blood pressure and may check the woman's reflexes and look at the back of her eyes with an ophthalmoscope (a handheld device that resembles a small flashlight).

PrintOpen table in new window
Some Causes and Features of Swelling During Late Pregnancy Cause Common Features* Tests Normal (physiologic) edema Similar and equal painless swelling (edema) in both legs that usually decreases when the woman lies on her left side A doctor's examination Deep vein thrombosis Swelling and pain in only one leg or calf Often tenderness, redness, and warmth in the affected area Sometimes risk factors for deep vein thrombosis If a blood clot travels to the lungs and blocks a blood vessel there (causing pulmonary embolism), chest pain and difficulty breathing Doppler ultrasonography of the affected leg to check for a blockage in the veins Sometimes a blood test to measure a substance released from blood clots (called D-dimer) If women have chest pain and difficulty breathing, CT of the chest or ventilation/perfusion (nuclear lung) scanning Preeclampsia Swelling in both feet and sometimes in the face and/or hands No tenderness, redness, or warmth in the swollen areas Sometimes headache, confusion, blurred vision, nausea or vomiting, or a reddish purple rash of tiny dots (which indicates bleeding in the skin) Sometimes risk factors for preeclampsia Measurement of blood pressure and the amount of protein in urine Cellulitis Swelling in one leg or calf and tenderness, redness, and warmth in the affected area Possibly pitting of the affected skin (resembling an orange peel) Often affecting a relatively small area Sometimes fever A doctor's examination *Features include symptoms and results of the doctor's examination. Features mentioned are typical but not always present.

Testing: If deep vein thrombosis is suspected, Doppler ultrasonography of the affected leg is done. This test can show disturbances in blood flow caused by blood clots in the leg veins.

If preeclampsia is suspected, the protein level is measured in a urine sample. High blood pressure plus a high protein level in urine indicates preeclampsia. If the diagnosis is unclear, the woman is asked to collect her urine for 24 hours, and protein is measured in that volume of urine. This measurement is more accurate.

Treatment

When swelling results from a disorder, that disorder is treated.

The swelling that occurs normally during pregnancy can be reduced by doing the following:

• Lying on the left side, which moves the uterus off the large vein that returns blood to the heart (inferior vena cava)
• Resting frequently with the legs elevated
• Wearing elastic support stockings
• Wearing loose clothing that does not restrict blood flow, particularly in the legs (for example, not wearing socks or stockings that have tight bands around the ankles or calves)

Key Points

• Some swelling in the legs and ankles is normal (physiologic) during pregnancy and occurs during the 3rd trimester.
• Doctors can identify serious causes of swelling based on results of a physical examination, blood pressure measurement, urine tests, and sometimes ultrasonography.
• If pregnancy itself is the cause, swelling can be reduced by lying on the left side, elevating the legs periodically, and wearing support stockings.

Last full review/revision May 2012 by R. Phillips Heine, MD; R. Phillips Heine, MD