Varicose veins are primarily caused by genetics, weight gain changes, overall lifestyle and family history. When trauma like this happens to veins, your veins become weak and damaged. Once the vein walls are damaged, your tiny one-way valves malfunction. Instead of your veins pumping blood directly back towards your heart, your vein values fail to close tightly. The result is that blood flows backward down towards your feet and pool. This increased pressure caused the veins to stretch and twist, therefore creating varicose veins!