Hello, thank you for your insights.Simple answer is that it's not possilbe. There is no way to guarantee re-entry to Canada. Whether she is allowed into Canada or not is always up to CBSA. Frequent border crossings increase the chances of issues.
Conisder finding an OBGYN in Canada and paying for the costs of the check-ups out of pocket. That's really the only solution if you want zero risk.
Can she stay in Canada though for the next 6-7 months? or do we apply for some sort of a visa for her?