The mother to be of course wouldn't be forced to have an abortion, nor would she not be given any time off. What it does mean however is that she can't collect any EI benefits and probably no income topoff from her employer, so you get 0$ for the time she is off. It would end up being an unpaid leave of absence.
There's really no such thing as a 'maternity leave payment'. It's Employment Insurance, but instead of collecting it because you got laid off, you're collecting it because you gave birth. And by law, your employer must have the same or similar position available to you upon your return.
This exact thing happened to my wife's acquaintances. She ended up pregnant 3 months after the birth of her first child. It was pretty tough for them for a couple of years.