These are bluish, tortuous and bulge when standing and collapse flat when the leg is horizontal or elevated. They may extend from the groin to the inside of the ankle and from the back of the knee into the calf. Varicose veins are caused by the loss of function of valves in the veins which are stretched apart and no longer prevent the blood in the veins flowing backwards towards the feet when standing. These kinds of veins often follow pregnancy. However, not every pregnant patient develops varicose veins. There has to be a genetic predisposition to them which is triggered by pregnancy, weight gain or ageing.