If a completely normal natural delivery, i would budget at least $5K for the delivery. Of course there is more for all the check-ups, blood work, ultra sounds etc during pregnancy which would be paid for out of pocket for each visit.
If any complications or c-section that requires an extended hospital stay, budget minimum $10K and possibly more. At least the baby will be covered by OHIP upon birth.
My suggestion, is to immediately begin looking for a midwife office in your area that is able to take her on as a patient. Midwife services should offer free services even to those without OHIP coverage. So this will cover lots of the pregnancy related checkups. A home delivery with a midwife would also be free, or a hospital delivery with a midwife instead of a doctor would be much cheaper (midwives have dedicated rooms in hospitals), and you can be discharged within hours after the delivery so no need for an overnight stay. The Midwife will then continue with home visit check-ups over the following weeks for mom and baby. The personal 24 hr care and attention they give you makes them a much better choice for routine pregnancies vs using doctors who will just be there during their work hours (in my opinion at least... we also used a midwife and had a great experience).
Since midwives are in very high demand, you need to start looking for one the second you find our you're pregnant else they will book up quickly.