Dear Raj,
First of all many thanks for your reply.
So let me get some further clarity. Since 15th May 2017 is my and my spouse's medical expiry (and visa expiry date), if I let London Visa Office know before 15 May 2017 that I am intending to land AFTER getting child delivered in my home country, they will just cancel my current visa/COPR and once child is born ask for new documents such as additional proof of funds, new medicals for me, spouse and child etc and issue me new visa/COPR if everything's in order?
My confusion reigns from the fact that once your landing date (15 May 2017 in my case) expires without you having landed in Canada, you go back to square one whereby you'll need to create a new Express Entry Profile, wait for an ITA and all that stuff again. But Raj, you're saying that in my case I will not go back to square one despite my visa going lapse by virtue of not landing before that date. All I would need to do is inform them of my decision to land after my child is delivered and they will basically put my application on hold until baby is born and then will ask all three of us to redo the medicals.
I hope I'm making sense to you and sorry in advance for picking your brain.