iStock Deep vein thrombosis (DVT) — a medical condition that occurs when a blood clot forms in a deep vein, usually in a leg — might be the most serious health risk you've never heard of. These clots can break off and lodge in your lungs to form a pulmonary embolism, which can be fatal. Situations that can lead to a clot run from the commonplace — like prolonged bed rest after surgery and long airplane flights — to the less-common, like pregnancy and genetic blood clot disorders. If you have obesity, or are a smoker, your risk of DVT increases. But there are steps you can take to minimize your risk — read on to find out how.