Well, its been over 6 years now since I have needed a maternity leave, but if I remember right it was just like any disability leave. I got 6 weeks paid leave, needed a doctor's ok to return to work, and received full pay and benefits while off work.
While six weeks is not really long enough, especially for first time mothers, in general it covers the physical recover from the birth. Where I work, many mothers take a longer period of time off, but unless they have vacation days, it is without pay. One lady had bedrest before the delivery and a C-section. Obviously, she will not be able to return after 6 weeks off.
We had one lady in a severe car accident while pregnant, and she blew through her benefits so quickly, and had injuries and a premature baby to care for. Other employees donated vacation hours to her, and were glad to do so although she never returned to work. Had it just been a normal healthy delivery she had planned to return, but with a premie baby and her own recovery, she wasn't going to be able to drive the distance to our clinic.
I think it is wrong to say you will return to work when you don't plan to. But how about the men and women who quickly use up their vacation time just before quitting? Or plan a 2 week vacation, and the day before they leave give 2 weeks notice, so they aren't there to help train the replacement? There are lots of people who don't treat their company fairly, and it does go both ways. I am fortunate to be at a good company. (Good thing, since we have had 4 girls born in the last 2 months, and two more babies on the way! And lots of flexibility for coming back part time.)