With my employer, my FMLA only kicked in after I used the accrued sick leave I wanted to use, so I took 4 weeks of sick leave, and then 12 weeks of unpaid FMLA leave, so my job was protected during that period.
They could have fired me, but I worked it out beforehand. I had to go on bedrest for a month before they were born, but they allowed me to stay out an additional 12 weeks (total of almost 17, actually).
I was paid the balance of my sick and vacation leave plus I had purchased a private short-term disability policy.