WARNING: CONTACT THE IRCC / EMBASSY IMMIGRATION SECTION.
Sorry for all caps, but by my read, you MUST contact them before departing. You probably will have to have your child ADDED to your spouse's PR application. (Which will mean a COPR and immigration visa for the infant as well, and possibly/probably extending validity of your spouse's as well). YOu'll need docs for the kid, a medical check, and probably other steps. On the positive side the child will be able to travel wtih your spouse and become a PR right away.
The reason is: your spouse's family composition has changed, she has a new, naturally born dependent. Read the COPR carefully, I believe it says that you must advise before landing.
While I could be wrong, trust me, you want to find this out BEFORE departing for airport.