Age: The development of spider veins may occur at any age but usually occurs between 18 and 35 years, and peaks between 50 and 60 years.[citation needed] Gender: It used to be thought that females were affected far more than males. However research has shown 79% of adult males and 88% of adult females have leg telangectasia (spider veins).[5] Pregnancy: Pregnancy is a key factor contributing to the formation of varicose and spider veins. The most important factor is circulating hormones that weaken vein walls.