Stretchy vs. Non-stretchy Fabrics

All of the diapers that I sewed up for this blog project were made with stretchy fabrics.  I tried to use similar fabrics for all of the patterns so that they could be compared apples-to-apples.

I picked one of the patterns that I have already tested (Trimsies, size small), and sewed one up with non-stretchy fabric (flannel) to compare.

At first glance they appear very similarly sized (stretchy is gray diaper; non-stretchy is vehicles diaper):

Then I fully stretched the wings to see how they compare.  I was expecting the stretchy one to be noticeable longer because the stretch of the fabric runs from wing-to-wing.  The wing span of the stretchy diaper measured 16", compared to 14.5" for the non-stretchy diaper.

I figured the rise of the diaper wouldn't be much different because the stretch of the fabric doesn't run from front-to-back.  But, I was very surprised to find out that there was a little more than an inch of difference in rise.  The stretchy diaper measured 14.5" long and the non-stretchy one measured 13.25"

So, if using non-stretchy diapers, then you might want to avoid any of the tiny newborn diapers, unless you are expecting a premature baby or a very small newborn.  If you were using fabric with moderate stretch (such as PUL or fleece), I would expect them to fall in between the non-stretchy & stretchy measurements.