Neither question is terribly clear - willostj: sounds like your baby was born to you, a Canadian PR, in the US. Is the baby's other parent a Canadian citizen? If the baby is a dual citizen, you just need to get his/her Canadian citizenship certificate and then you can bring him/her back to Canada. If not, you will have to sponsor the baby for PR and it will be up to the IO at the Canadian port of entry as to whether or not your baby will be allowed to enter Canada before s/he has been granted PR status. And, as a PR, you will not be able to apply to sponsor your child unless you are in Canada yourself.
martha: same situation for you. It all depends on whether your baby's other parent is a Canadian citizen or not. If so, the baby is a Canadian citizen - if not, s/he needs to be sponsored and you cannot sponsor, as a PR, while outside Canada.