These Paco pants are being modeled by a 6-month-old baby!
The maker reports:
I used baby’s real measurements taken over a diaper. The pattern pieces looked ridiculous (because baby proportions are ridiculous) but it worked great. The only setting I altered was changing ankle/hem width to 10%. I made an extra wide waistband with no elastic — the waistband piece was about 38 x 10cm.