If you're 7 or 8 months pregnant, there's a chance you could be refused entry. There's nothing you can do or carry to guarantee that you will be allowed into Canada. That decision is entirely at the discretion of the immigration officer you encounter. So if you decide to come, understand there's a risk you could be sent home.
You should carry proof that you have sufficient funds to pay for the baby to be delivered in Canada. (This means you should be able to show a bank balance of over $10K Canadian).
