This was a cute little green polka dot onesie that got to short wat to fast for my granddaughter. So I cut off the bottom part and took and sewed some bias tape to the bottom of the tonesie top, then I turned under the bias tape for the hem and sewed it up. Now... because this was a jersey style fabric, I had to increase the size or length of the stitch on the sewing machine, so not to pucker or ripple the fabric which would affect the finished look. It can be a little hard to sew on this type of fabric if it is your first time... one wouldn't think about increaseing the stitch length.
This is such a cute little 3-6 month onesie... I think we will keep it for her dolls. Doll clothes can be hard to come by if you don't plan when you have the infant size clothes around anymore, when they reach the age for playing with dolls!