Blood Clot Risk During Pregnancy (DVT)
The short answer
Pregnancy increases the risk of blood clots (venous thromboembolism or VTE) by 4-5 times due to increased clotting factors, slower blood flow, and vein compression from the growing uterus. While the overall risk is still low (about 1-2 per 1,000 pregnancies), awareness of symptoms is important because blood clots can be life-threatening if untreated.
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By Age
What to expect by age
Blood clot risk is elevated from early pregnancy. Risk factors include previous blood clots, family history, obesity, immobility, cesarean delivery, and certain genetic clotting disorders. If you have risk factors, your provider may recommend blood thinners (low-molecular-weight heparin). Stay active and hydrated.
Risk increases as the uterus puts maximum pressure on pelvic veins. Avoid sitting or standing for long periods. On long car or plane trips, move regularly and stay hydrated. Compression stockings can help. Be aware of DVT symptoms: swelling, pain, warmth, and redness in one leg (usually the calf).
Blood clot risk is highest in the first 6 weeks after delivery, especially after cesarean. Get moving as soon as safely possible after delivery. Your provider may recommend compression stockings or blood thinners if you have additional risk factors. VTE is a leading cause of maternal mortality, making awareness critical.
What Should You Do?
When to take action
- Mild bilateral (both legs) swelling in late pregnancy is normal and is not a clot sign
- Varicose veins without warmth, redness, or pain are common and not typically a clot
- You have a personal or family history of blood clots or clotting disorders
- You will be immobile for extended periods (bed rest, long travel)
- You have multiple risk factors for blood clots
- Swelling, pain, warmth, or redness in ONE leg (especially the calf) that is different from the other leg - possible DVT
- Sudden shortness of breath, chest pain, rapid heartbeat, or coughing up blood - possible pulmonary embolism - call 911 immediately
- These are medical emergencies that require immediate evaluation
Sources
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Trust your instincts. If something feels wrong, reach out to your pediatrician.
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Related Maternal Concerns
Varicose Veins in Pregnancy
Varicose veins are swollen, twisted veins that commonly appear in the legs during pregnancy. They affect up to 40% of pregnant people and are caused by increased blood volume, hormonal changes that relax vein walls, and pressure from the growing uterus on pelvic veins. They are usually a cosmetic concern but can cause aching or discomfort.
Swelling in Feet, Ankles, and Hands During Pregnancy
Mild to moderate swelling (edema) in the feet, ankles, and hands is very common in pregnancy, affecting about 80% of pregnant people. It is caused by increased blood volume and fluid retention, and it is usually harmless. However, sudden or severe swelling, especially in the face and hands, can be a warning sign of preeclampsia.
Air Travel While Pregnant
Air travel is generally safe for most pregnant people through 36 weeks of pregnancy (earlier for international flights or some airlines). The cabin pressure, altitude, and radiation exposure on commercial flights do not pose risks to healthy pregnancies. The main concern is the increased risk of blood clots from prolonged sitting, which can be mitigated by walking, stretching, and staying hydrated.
Dealing with Abnormal Prenatal Screening Results
An abnormal prenatal screening result can be terrifying, but it is important to understand that screening tests are designed to cast a wide net and have significant false-positive rates. Most people with abnormal screening results go on to have healthy babies after further testing confirms the baby is fine. An abnormal screening is a reason for more information, not a diagnosis.
Pregnancy Over 35 (Advanced Maternal Age)
While pregnancy after 35 carries some increased risks (including chromosomal abnormalities, gestational diabetes, and hypertension), the vast majority of people over 35 have healthy pregnancies and healthy babies. The term "geriatric pregnancy" is outdated and does not reflect reality. With appropriate prenatal care and monitoring, outcomes are excellent.
Amniocentesis Questions and Fears
Amniocentesis is a diagnostic test performed between 15-20 weeks that analyzes amniotic fluid to detect chromosomal conditions and genetic disorders with over 99% accuracy. The risk of pregnancy loss from the procedure is approximately 1 in 500-1,000 when performed by an experienced provider. Understanding the actual risks can help you make an informed decision.