My little girl was over due and she weighed 5 pounds and 11 ounces. I'm small framed and so is her dad. She was perfectly healthy.
My baby was born almost three weeks ago at 37 weeks, she came out of nowhere, was 5lbs, because of her weight and because it was at the beginning of 37 weeks she was considered preemie
Weight has nothing really to do with that. Usually its based off what week gestation baby was born, what organs function, breathing, ability to eat, reflexs, etc...
That is a little small for the average baby, but prematurity would be indicated by other things besides just weight alone. How developed are the lungs, is there any body fat, things like that. Talk to the baby's pediatrician (if this is your baby) to get more insight on this question.