If you're considered high risk, then it's not uncommon at all. Some women are put on bed rest at 20 weeks or earlier.
I was personally taken off of work by my doctor in the middle of .june for complications with my hip, and I didn't give birth until .august 10th. I wasn't considered high risk, either.
If you're off of work until you give birth, I suggest finding something to occupy your time. You will very quickly start getting bored! Books, tv shows, knitting or cross stitching, playing games online, etc... they can help save your sanity!