I had that with my daughter. She came through great. She'll be 9 in November and is perfect. Has never been an issue.
My last had that. It made no difference what so ever
I was told the same thing but all the doctors I've talked to have told me it's actually more common than we think and not to worry about it. Just like you, they said they will do a little extra monitoring to make sure babies weight stays where it should. So far so good for me and I'm 23 weeks and she's weighing a pound.