What causes small blood vessels or vein to show under the eye area on the skin?

I never had this problem before, but after I had my baby I noticed under my right eye there is a veiny type looking blood vessel. I%26#039;m only 23 and I have no clue what is causing it to appear there. Any suggestions? I cover it up all the time with concealer, but that%26#039;s a big pain in the butt!|||lack of oxygen in the blood,like if you smoke alot that deprives the blood of the oxygen it requires!