Pattern is constructed in the round and includes instructions for how to alter the size. A back measurement taken from armpit to armpit is required in order to adjust the size.
You may also use a heavier yarn and a larger hook to obtain a bigger size (eg. Chunky with an 8mm hook for adults)

Pattern is written for approx 3-6 month size.

Larger sizes will have more rows of plain treble crochet, as the motif forms part of the back and the edging on the front.

Pattern is written in UK terms.