Blood Clots in Women: Risk Factors and Warning Signs You Should Know

A blood clot is your body's normal response to injury — a plug that stops bleeding and then dissolves once the job is done. Venous thromboembolism, or VTE, is what happens when that same clotting process starts somewhere it shouldn't, inside a vein where blood should simply be flowing.

It affects up to 900,000 Americans a year, and women face several risk factors — hormonal birth control, pregnancy, the postpartum period — that men simply don't. Knowing what raises your personal risk, and which symptoms need urgent attention, is the most useful protection available.

What Raises a Woman's Risk for Blood Clots?

Estrogen is a common thread. Hormonal birth control that contains estrogen raises clotting risk, and hormone replacement therapy carries a similar effect. The increase is real but modest — pregnancy itself raises clotting risk more than birth control does, so the comparison matters when weighing options with a provider.

Pregnancy and the months afterward carry the highest hormone-related risk: women are about five times more likely to develop a dangerous blood clot during pregnancy, childbirth, or the three months after delivery, and a pulmonary embolism is one of the most common causes of pregnancy-related death in the United States. A C-section nearly doubles that risk further.

Beyond hormones, the same risk factors that apply to anyone still apply: recent hospitalization or surgery, prolonged immobility (long flights, bed rest, a cast), obesity, smoking, older age, active cancer or cancer treatment, and a personal or family history of blood clots or a genetic clotting disorder.

What Are the Warning Signs of a Blood Clot in the Leg?

A deep vein thrombosis (DVT) typically causes swelling in the leg or arm, pain or tenderness that's hard to explain, skin that feels warm to the touch, and redness or discoloration over the affected area. About half of people with a DVT have no noticeable symptoms at all, which is part of why knowing your risk factors matters as much as watching for symptoms.

What Are the Warning Signs of a Pulmonary Embolism?

A pulmonary embolism happens when part of a clot breaks loose and travels to the lungs, and it's a medical emergency. Warning signs include sudden shortness of breath, chest pain or discomfort that worsens with a deep breath or cough, a rapid or irregular heartbeat, lightheadedness or fainting, and coughing up blood. Sudden death is the first symptom in roughly one in four people who experience a pulmonary embolism, which is why these symptoms call for emergency care rather than a wait-and-see approach.

If you or someone else experiences sudden shortness of breath, chest pain, or fainting alongside leg swelling or pain, call 911 or go to the nearest emergency room right away.

Can Blood Clots Be Prevented?

Avoiding a sedentary lifestyle is one of the most consistently recommended steps: moving your legs during long flights or car rides, getting up and walking after surgery as soon as it's approved, and staying hydrated all support healthy blood flow. Knowing your family history matters too, since a genetic clotting disorder changes the risk calculation for things like hormonal birth control or long travel.

Tracking Circulation Matters More During High-Risk Times

Circulation naturally slows during long periods of sitting, after surgery, and during pregnancy — the same stretches when clot risk rises. That makes those windows a reasonable time to pay closer attention to how your circulation feels day to day, alongside the prevention steps above.

To be clear: Ruby does not detect, diagnose, or rule out blood clots, DVT, or pulmonary embolism. The Ruby app estimates a Circulation Score from a fingernail selfie as a general wellness check-in — it is not a substitute for medical evaluation, and it should never be used to decide whether symptoms need urgent care.

Always take symptoms of a possible blood clot seriously and contact a healthcare provider or emergency services rather than waiting to see how you feel.

None of this is meant to make blood clots feel like they're lurking around every corner. Most people who fly, take hormonal birth control, or have surgery never develop one.

But if you're starting a new hormonal medication, planning a long flight, or recovering from surgery, ask your provider whether your personal risk factors call for any extra precautions.

Common FAQs

What raises a woman's risk for blood clots? Estrogen-containing birth control, hormone replacement therapy, pregnancy and the postpartum period, recent surgery or hospitalization, prolonged immobility, obesity, smoking, and a family history of blood clots all increase risk.
What are the warning signs of a DVT? Swelling, pain or tenderness, warmth, and redness or discoloration in the affected leg or arm. About half of people with a DVT have no symptoms at all.
What are the warning signs of a pulmonary embolism, and is it an emergency? Yes, it's a medical emergency. Sudden shortness of breath, chest pain that worsens with breathing, a rapid heartbeat, lightheadedness, fainting, or coughing up blood all call for immediate emergency care.
Does birth control cause blood clots? Estrogen-containing birth control does raise clotting risk, but the increase is smaller than the risk increase from pregnancy itself.
Can blood clots be prevented? Staying active during long travel or after surgery, staying hydrated, and knowing your personal and family risk factors are the most consistently recommended prevention steps.

References

1. CDC — Data and Statistics on Venous Thromboembolism: https://www.cdc.gov/blood-clots/data-research/facts-stats/

2. CDC — About Venous Thromboembolism (Blood Clots): https://www.cdc.gov/blood-clots/about/index.html

3. Mayo Clinic — Deep Vein Thrombosis (DVT): Symptoms & Causes: https://www.mayoclinic.org/diseases-conditions/deep-vein-thrombosis/symptoms-causes/syc-20352557

4. Cleveland Clinic — Does Birth Control Cause Blood Clots?: https://health.clevelandclinic.org/yes-your-birth-control-could-make-you-more-likely-to-have-a-blood-clot

5. CDC — Expecting or Recently Had a Baby? Learn about Blood Clots: https://www.cdc.gov/blood-clots/toolkit/pregnancy-infographic.html

6. CDC — Understanding Your Risk for Blood Clots with Travel: https://www.cdc.gov/blood-clots/risk-factors/travel.html