Others will correct me but if you land before the baby is born then believe you do not have to do anything given until the baby is born it would not be considered an additional family member or dependant requiring to be included on your PR application. In fact assuming you land before the baby is born and is born in Canada it will be a citizen, even then no need to inform IRCc given you would be a PR then.
Be aware though and there are other posts on this that there are qualifying periods for health cover so you may find you need to be prepared to self fund the delivery. So you need to investigate any qualifying residency requirements for health cover for example Ontario is 3 months which assuming a November delivery you may just qualify if landing by July.
