First thing, it is more common to have single umbilical artery if pregnant w/a girl, I take it you don't know the sex :)...I don't want you to worry you by any means, but the doctors should be spending more time explaining the possible complications from this. My dr., just like yours, said no biggie and ran out the door. I had the same thing, obviously, and I looked up single umbilical artery on the internet. Check it out. Like the articles will tell you, 2/3 of babies with SUA are born with no complications whatsoever. My daughter, however, was born with something called "vater association" which is linked to SUA. Two days after birth, 11-21-08, she had to have surgery to connect her asophogas to her stomach, has one kidney, and a small hole in her heart, correctable when she gets a little older. She is doing great now, she is a little small, but no biggie.. It was a real whirlwind at first...I hope you don't experience any of this..Talk to your doctor but please, please, please don't worry yourself sick, not good for you or the baby, just thought I'd share my experience w/you..Take good care and good luck with everything...