Pregnancy

One Swollen, Painful Leg: Rule Out a Clot

Save

One leg that turns swollen, painful, warm, or red during pregnancy or the weeks after birth can signal a deep vein blood clot. Pregnancy raises clot risk several-fold, and left-leg swelling is a classic clue. It needs urgent, same-day evaluation, and any chest pain or breathlessness means calling 911.

Last updated: July 2026

If this is happening now

Seek urgent, same-day care for one swollen, painful leg in pregnancy or postpartum, and call 911 or go to the nearest emergency room immediately if you also have chest pain, sudden breathlessness, or coughing up blood, because a clot may have traveled to the lungs.

Care like this may require 911 or emergency services. Gale doesn't schedule appointments for emergencies — emergency care comes first; scheduled follow-up can wait until you're safe.

What to do right now

Contact your obstetric team or urgent care the same day if one leg becomes swollen, painful, warm, or red in pregnancy, and call 911 if chest pain or breathlessness develops 1. A leg ultrasound can usually confirm or rule out a deep vein clot quickly, and treatment with blood thinners can start promptly if needed. Note which leg is affected, when the swelling began, and whether the calf is tender, because blood clot symptoms in the leg guide the workup. The American College of Obstetricians and Gynecologists treats suspected clots in pregnancy as urgent, because delay raises the risk of a clot reaching the lungs 1.

Why is a one-sided swollen leg different?

Swelling in both legs and feet is common and usually benign in pregnancy, driven by fluid retention and the growing uterus pressing on veins. A clot is different: it typically causes swelling, pain, warmth, or redness in just one leg, often the calf. Up to about 80 percent of pregnancy-related deep vein clots occur in the left leg, because of how the pelvic veins are compressed 1. Unlike clot risk on long flights, which is temporary, the raised risk in pregnancy lasts throughout and beyond it. Persistent one-sided calf pain and swelling, especially with tenderness, is the pattern that warrants urgent evaluation.

Why does pregnancy raise the risk of clots?

Pregnancy shifts the blood toward clotting to prepare for the blood loss of childbirth, which is protective at birth but raises clot risk beforehand. According to ACOG, pregnancy increases the risk of venous clots roughly four to five times compared with not being pregnant, though the overall chance in any one pregnancy is still low, on the order of 1 in 1000 1. The growing uterus slows blood flow from the legs, and reduced movement, dehydration, or a prior clot add further risk 1. Recognizing other pregnancy warning signs alongside leg symptoms helps you and your team judge urgency. The higher baseline risk is exactly why one-sided leg symptoms are taken seriously.

When is leg swelling in pregnancy just normal?

Mild, symmetrical swelling of both feet and ankles that improves with rest and leg elevation is a normal part of many pregnancies, particularly in the third trimester. The picture changes when swelling is one-sided, painful, or sudden, or when it appears in the weeks after delivery. Clot risk does not end at birth; it is actually highest in the first six weeks postpartum, so a swollen, painful leg during recovery deserves the same urgency as during pregnancy 12. Across the reproductive years, the same warning applies whether the pregnancy is a teenager's first or a later pregnancy after age 35, since both carry the pregnancy-related rise in clotting. Standard routine prenatal visits also include an assessment of clot risk factors early in pregnancy 3.

When a swollen, painful leg needs same-day care

A leg that becomes swollen, painful, warm, or red on one side during pregnancy or the postpartum weeks is a reason to seek urgent, same-day evaluation 1. A deep vein clot is treatable, but if part of it travels to the lungs it becomes a pulmonary embolism — a leading cause of pregnancy-related death that needs a 911 response. Chest pain, sudden breathlessness, coughing up blood, or a racing heart alongside a swollen leg means calling 911 right away 1. There is no safe way to distinguish a clot from harmless swelling at home. Prompt ultrasound is the step that protects you and the pregnancy.

Common questions

Swelling in both legs and feet is very common in pregnancy and usually reflects normal fluid retention rather than a clot. A deep vein clot more often causes swelling, pain, warmth, or redness in just one leg. If both legs are mildly and equally swollen and improve with rest and elevation, that is typically benign, but new one-sided swelling or pain deserves an urgent check.

The left leg. Because of how the pelvic veins are positioned and compressed during pregnancy, the large majority of pregnancy-related deep vein clots occur on the left side. That does not mean a right-leg clot is impossible, so one-sided swelling or pain in either leg is worth prompt evaluation.

Usually with an ultrasound of the leg, which is safe in pregnancy and can show whether a deep vein is blocked. If a clot is found, treatment is typically an injectable blood thinner that does not cross the placenta. If lung symptoms are present, additional imaging may be needed urgently.

Not right away. The risk of clots is actually highest in the first several weeks after delivery, then gradually returns toward baseline. New leg swelling and pain, or any chest pain or breathlessness during recovery, should be treated with the same urgency as during pregnancy.

Related

When a swollen leg in pregnancy is an emergency

  • —Swelling, pain, warmth, or redness in one leg during pregnancy or the weeks after birth is a reason to seek urgent, same-day medical evaluation.
  • —Chest pain, sudden shortness of breath, coughing up blood, or a racing heart is a reason to call 911 immediately, because a clot may have reached the lungs.
  • —A calf that is tender, hard, or noticeably larger than the other side is a reason to contact your clinician the same day.
  • —Feeling faint, dizzy, or unusually short of breath with a swollen leg is a reason to go to the nearest emergency room right away.

Seek urgent, same-day care for one swollen, painful leg in pregnancy or postpartum, and call 911 or go to the nearest emergency room immediately if you also have chest pain, sudden breathlessness, or coughing up blood, because a clot may have traveled to the lungs.

This article is general health education, not medical advice. Whether leg swelling in your pregnancy reflects a deep vein clot or a normal change can only be determined by an obstetric or emergency clinician using an examination and, when needed, an ultrasound.

References

  1. 1.American College of Obstetricians and Gynecologists (2018). ACOG Practice Bulletin No. 196: Thromboembolism in Pregnancy. Obstetrics & Gynecology. doi:10.1097/AOG.0000000000002706 ✓Elevated venous thromboembolism risk in pregnancy (roughly four- to five-fold), left-leg predominance of deep vein clots, urgent evaluation and ultrasound for suspected clots, and pulmonary embolism as a leading cause of maternal death.
  2. 2.American College of Obstetricians and Gynecologists (2018). ACOG Committee Opinion No. 736: Optimizing Postpartum Care. Obstetrics & Gynecology. doi:10.1097/AOG.0000000000002633 ✓Postpartum warning signs to report promptly, including new leg swelling and pain, during the high-risk early recovery period.
  3. 3.National Institute for Health and Care Excellence (2024). Antenatal care (NG201). National Institute for Health and Care Excellence (NICE). link ✓Antenatal care includes early assessment of venous thromboembolism risk factors in pregnancy.

3 sources, numbered by first appearance. General health information, not medical advice. AI-assisted editorial content — every citation independently verified. Editorial policy

← Back to the health library