The causes of varicose veins: 1, weakness of the vein wall and valve defects: the vein wall is relatively weak and can expand under the action of venous pressure, and the expansion at the valve sinus leads to the inability of the original venous valves to close closely, resulting in relative valve insufficiency and backflow of blood. Valve dysplasia or absence, also can not play an effective role in preventing backflow, leading to the onset. 2, venous pressure persistently elevated: venous blood itself due to the role of gravity, a certain pressure on the valve, under normal circumstances will not cause damage, but when the venous pressure continues to rise, the valve will withstand excessive pressure, gradually relaxation, prolapse, so that the closure is incomplete. This is mostly seen in long-term standing work, heavy physical labor, pregnancy, chronic cough, long-term constipation, etc. 3, followed by age, gender: because the limb venous pressure only in the body length up to the highest when the highest pressure, the body before puberty is not high, so the caliber of veins is small, all can prevent venous dilation, so although there are suffering from serious varicose veins before 30 years old, but most of them are with age, the vein wall and valve gradually lose its tension, the symptoms increase forcing patients to seek medical attention. Varicose veins are more common in women, probably because pregnancy can trigger or exacerbate them. However, in women without pregnancy, the incidence is higher than in men (male:female=1:3), probably because of the wider pelvis, the excessive curvature of the vascular structures and the increased congestion of the veins in the pelvis during menstruation, pregnancy and menopause. Another reason why varicose veins are prone to occur during pregnancy is because the tension of the superficial veins of the extremities is reduced during pregnancy, making them prone to dilatation, a condition that can be restored after delivery.