Hi,
We recently ( wife and myself ) received landing papers and passports with immigrant visas. We are going to have baby in few weeks( new addition to the family ) and We cannot land before baby´s birth on health and insurance reasons.

So I want to know whether we can land with baby as visitor on US passport and sponsor baby later from Canada. Are we going to have any issues at the Port of Entry, do they let us in.
I wrote to Immigration authorities about my concern after receiving passports and they wrote back saying that they cannot add baby now as my case got finalized already. They mentioned in the letter to land before the expiry of visas or else return the unused visas and COPR docs for return of landing fee. I am worried to write to them again.
I am thinking of hiring lawer but do not know how lawer is going influence immigration authorities.

Please advise.

If you read the documentation you received from Canadian Immigration, you can not go to Canada after having a change in family status like having a baby.

You have 3 choices

1) You and your wife land and come back to US immediately
2) You start your case again from scrtach after baby is born
3) If you are the principal you land alone before the baby comes if you wife is not in a position to travel.

In case # 3 wife will not be allowed to land later. When you move to Canada you will have to sponsor her.