Photo from Stitch/Interweave
Description by Stitch Magazine: "Inspired by the traditional kimono, this sleep set is perfect for active toddlers. The ribbed-knit cuffs on the sleeves and legs fold up and down for extra growing room, and the comfortable elastic-free waistband gets its stretch from a little spandex in the knit." Designed by Bonnie Ferguson
The pdf download includes the pattern pieces for the shirt and the pants, and it provides the dimensions for the various bands of ribbing. In this post from the pattern designer's blog, you can see that there is ribbing around the waist as well. The only thing I wasn't sure about was the size of the seam allowance (which I assumed was included in the pattern), so I just went with 1/2" and that worked well for me.
I used a mix of fabrics from the stash - the striped fabric came from a thrifted t-shirt, the solid in the bodice is leftover from when I made these leggings, and the rib knit is from Joann, purchased in anticipation of one day needing it for toddler-wear.
L is currently nearly 20 pounds and 30 inches tall - I made the 12 month size and there is plenty of room for growing, which is a plus.
Stitch Magazine offers the pattern in sizes newborn - 12 months, and Bonnie Ferguson added sizes 18 months - 5T on her blog - how cool is that? I definitely see more of these in my future, and they are a fun way to use scraps and repurpose old tees.