There are two main reasons why spider veins and varicose veins are not treated during pregnancy in the United States. First, female hormones (progesterone) that cause veins to dilate are elevated during pregnancy and cause abnormal veins to increase during pregnancy. Some of these veins will recede after delivery, when hormones go back to normal levels. Also, blood volume is increased during pregnancy. It makes sense to wait until after the delivery to treat the abnormal veins that remain. The second reason is mediolegal. While there is no evidence that injecting spider veins during pregnancy causes harm to the fetus, the highly litigious society we live in makes treatment unreasonable during pregnancy. One final note. If you have problems with leg veins, aching, or swelling after pregnancy, get the veins treated before your next pregnancy. They will only get worse with each pregnancy, and your suffering will get worse. You do not need to wait until you complete all your pregnancies.