Although pregnancy is one of the leading causes of varicose veins, there is no reason to continue suffering with the symptoms through additional pregnancies.
Actually, pursuing treatment prior to any future pregnancies is the best scenario because it will make your next pregnancy more tolerable if you are symptomatic (pain, swelling, etc.). Also, in most cases, it will prevent the progression of the vein problems you might otherwise experience if you should avoid treatment until you feel you are finished having children.