Infants and toddlers almost always have an elastic waistband for pants and skirts. The elastic waist allows for comfort and growth. Often, there is an elasticized back waist because children have a larger front waist (from a protruding belly) than back waist. The patterns are cut so that the front is a little wider than the back waist. The back waist then requires either darts or elastic.
I am working on my bloomers/pantaloons and trying to determine an appropriate elastic waist measurement. Generally the elastic should be cut the same size as the waist and overlapped one inch. The finished, relaxed measurement will be one inch smaller than the actual waist. Be sure the elastic stretches to the full hip measurement (and maybe a little more for easier diaper changes).
Anyway, while browsing the web I ran across this awesome idea for elastic waist pants from BabyGap. The idea is actually brilliant and I want to get my hands on a pair to see how they are made. The elastic waist is designed so that you can pull the elastic and button it for a narrower fit. Brilliant. I wonder how well it works in practice. Unfortunately the nearest BabyGap is over 100 miles away..... Anyone out there in Blogland have a pair and can tell us all about these pants in use?
BTW, the BabyGap link also has a size chart. Notice that BabyGap has published foot measurements for booties, hat, and mitten sizes. Hmmm....