In my district (and most others) you are permitted to take up to six weeks following the birth or adoption of your child. If you don't have enough sick days saved up (as I did not), you can take the leave unpaid. I was lucky enough to find myself unexpectedly pregnant my first year of teaching. Obviously, I did not have enough days saved up, so I took part of my leave unpaid.
The real issue with maternity leave is that your students are still there and they still need to learn. You're allowed to choose your own substitute, though most schools have a list of subs they'd like you to use. My substitute was a friend from college who also happened to be a preferred sub at my school. Despite my leave being partially unpaid, I still technically had to work during my leave.
The first thing I needed to do was make subwork. This was the tricky part. See, due dates are not always accurate. In fact, they are rarely accurate. I had to make six weeks worth of subwork and then make it fluid so that it could cover whenever I went into labor. The trick I used was to plan six weeks in advance with detailed notes. As I finished a week, I'd remove those plans and create new ones. I didn't have to do this very long as I ended up delivering early. I was due at the end of April, but went into labor the day Spring Break started, just over three weeks early. Because of the timing, my sub only needed to use five weeks of the work that I had created.
While I was on leave, my students took one of those fantastic ORQs. About two weeks postpartum, I drove to school to pick up the tests. I graded them and turned around and returned them the following day.
Our gradebooks are entirely electronic on a website called InfiniteCampus. Only I could log on and put in grades for my students. It was frowned upon to share your log on with your sub, so she emailed me their grades once a week and I put those in when I received them.
Parents can also email teachers. I received emails from parents that I still had to answer. I had one guy email me a couple times each week wanting me to get answers right that second about how his daughter was behaving for the sub. I could email my sub, but she didn't reply that quickly. He didn't seem to understand why I was taking so long to reply, even after I told him I had a newborn at home.
You know that old saying "Sleep when the baby sleeps"? My thing was "Work when the baby sleeps." Thankfully, my son was born close enough to the end of the year that I only had to return to work for four weeks before summer break began. And then I got to spend my summer going to professional developments and planning for the next school year. A teacher's work is never done, but thankfully it's very rewarding work.