Its up to you..let me give my 2 cents
Option 1: If you get PPR and travel with spouse before child birth --No problem, You will have the baby there and get his/her PPR sorted over there.
Option 2: If you give birth / or decide not to go before birth,once you give birth,raise a CSE and inform of new addition,a medical for the bay plus the passport will be requested.If you have already gotten your COPR,it will be requested to be submitted and a fresh one will be issued to all of you guys.
Option 3: If you get PPR and passport request and baby is close,you can immediately inform them you are expecting and would like to add baby,in that case,they can give you say 60days to complete all documentation which would include new born.With this,you wont have to send passports back and forth.
Others can add more inputs.Everything written is based on my understanding and not specifically FACTS.