I made a fun, cute and flirty maternity skirt that I made from a regular skirt. Now it's your turn. Here's how to turn any skirt into a maternity skirt. First you need a stretchy cami. Cut off the top. Cut off the top of the skirt at a place where it will be able to just go over your hips. Keep it a tad snug. I cut mine off just underneath the zipper; so I needed to gather it to the correct width. To gather, I zigzagged over a piece of floss and pulled the thread. Since my skirt was so wide, I quartered it and gathered the four sections separately. Much easier than going all the way around. Matching raw edges and side seams with right sides together, pin the cami piece you cut to the the skirt. I used lots of pins to keep my gathers in place. Sew with a zigzag stitch, but don't stretch the material as you sew or it may be too loose.
(Quick fix: If your skirt turns out to be too loose and slips down, just sew up the side seams of the band till you have a comfortable fit.) Tip: If the skirt you are using for this project has gathers or pleats, before you cut off the top, straight stitch all the way around just below the cut line so that you maintain those gathers or pleats; otherwise, you'll have to put them back in. This will save you a lot of time and headache.
Variation (Not pictured) If you prefer a more narrow band, you can also fold down the attached piece when wearing or fold down and stitch.
You could probably do this to your skirts even if you aren't pregnant if you want a more comfortable waist band and to allow for fluctuations in weight.
This is a very quick project. I did this to around seven skirts that I picked up at a thrift store. They were having a sale, all you could stuff in a bag for $10. Made my day.