At 20 weeks, that's a possibly 5-month old fetus, with potential for viable birth (given modern technology).  I know a couple who had labour induced at that point since the mother would have lost the child otherwise.  While it's not healthy to be so premature,  I think allowing abortion at 20 (or 24!) weeks is more radical than banning it at that late stage.  I'm fairly sure that it's not allowed in Canada unless the mother's life is threatened or the fetus irreparably damaged. 

So quite frankly, I don't see the point - at least in Canada - of getting all worked up about this particular ban.  The right to abortion isn't being taken away, only what seems to me a reasonable limit to how far along a woman may be before getting the procedure.