This is a pattern for a envelope onesie. The sizes are from 50-92.
To make this onesie you need followin length of the fabric:
50 - 50cm
56 - 50cm
62 - 55cm
68 - 55cm
74 - 55cm
80 - 60cm
For more instructions about how to make this onesie (in swedish) visit: https://hallonsmuladesign.files.wordpress.com/2016/02/tutorial-kuvertbody-stl-50-921.pdf