Doctors say that genetics and gender play the biggest role. If you are a woman and one of your parents had varicose veins, then you probably have them, too, especially if you have had multiple pregnancies. Actually, the heart has an ally in the upward-pumping process. Every contraction of your calf muscles helps push blood back toward your heart. In fact, almost 90 percent of all venous blood leaves your legs through the deep veins by the contraction of your muscles.
Doctors call it the calf muscle pump or peripheral heart.
As the blood ascends your veins, a series of valves prevent it from flowing back down. They are like swinging doors going into a saloon, except they only open one way, says Kevin Welch, M.D., dermatologist with the Medical Center of Pensacola in Florida. Varicose veins start when the circulation slows, usually because of the lack of muscular activity. The blood begins to pool and stretch the walls of the vein. The added pressure in the distended vein pushes on the valve, eventually forcing the saloon doors to open the wrong way.