If you don't get asked in the airport how long you were gone, I am sure you have to fill it out on your customs card. Maybe you will get through but when you apply later to have your PR card renewed and you fill out how many days you were gone from Canada, you will have a problem.
This is from the immigration Canada website though:
If you are unable to meet the residency obligation, we will consider any compelling humanitarian and compassionate factors in your individual circumstances that may justify the retention of permanent resident status.see
http://www.cic.gc.ca/english/information/applications/guides/5445EA.aspNow, I don't know if they ever really use this clause or if they will tell you that you could have come back and left the baby with relatives or you could have come back and sent your husband to take care of the baby but it's worth a shot. Otherwise, maybe your husband will have to sponsor you again.