I am guessing that you are covered by IMSS since you said it came from your husband's work. With IMSS there are no additional charges for covered services. Maternity is excluded for the first 6 months or a year, I don't remember which. Assuming you have been with them for awhile, you should be covered. And if you are covered, there should be no expenses. Language can be a problem. In two years with IMSS, including a many visits to the admin office due to mistakes that I made, and a few visits to doctors and dentists, I have never met anyone that spoke a word of English. My spanish is almost passable but by no stretch of the imagination good. So I never understand things as well as I would like, nor can I ask as many questions as I would like.
Regarding the citizenship status of your future child, I don't know. That kind of information should be easy to find, however, either from google or a call to the Canadian consulate/embassy.