The medicines which can cause spider veins are the ones which include estrogen and progesterone. Birth control pills can also lead to the formation of these veins. Since all these medicines cause hormonal changes in the body thus they can be a reason for the appearance of these veins. During pregnancy when medicines containing progesterone and estrogen are taken the level of hormones in the body are increased which causes the increased volume of blood in the body. Since the volume of blood is more it causes the veins to become enlarge and form spider veins.

 Moreover the enlarged size of uterus also puts pressure on the veins. These spider veins which occur due to hormonal increment after taking medicines generally fades after the birth of the child when the medication is stopped. Similarly birth control pills also cause spider veins as it contains estrogen and progesterone. Moreover, these pills also increase weight and this excess weight causes pressure on the veins, dilates them and forms spider veins. Besides these medicines there are various other reasons which cause the formation of these veins and these include leg injury, prolonged standing, advancing age, sedentary lifestyle, exposure to ultraviolet rays and many others.