They can't fire you, they're just trying to scare you. You could sue their tails off if they fired you, so they just want you to think they can fire you so you'll come into work. You better listen to those doctor's orders girl...it's a very serious matter!
They cant fire you. Trust me im in a similar position
You don't have to quit just because your boss is threatening to fire you. Especially since you have a doctor's note, it will be illegal to do so.
If you have a doc note by law they can't fire you but do what is best for you and baby. I would just give them a lovely reminder of that doctor note. Might change their mind a lil bit.