I'm a small person, and finding maternity pants that fit me is difficult. I got sick of looking frumpy in baggy butt jeans, and wanted to look cute, again. I found this tutorial for making maternity pants out of regular ones. I followed it with this pair of pants.
Unfortunately, they didn't turn out super. The instructions have you cut all the way below the zipper. This probably works great if you are farther along. My belly just isn't quite big enough to hold up a pair of pants with the waist cut out. So, I adapted the tutorial with these.