I seldom make any quilt smaller than width of fabric square but I prefer 48 X 60 for a baby quilt. They grow so fast and if we put our love and skills to work into a quilt, let's let those kiddos have years of use from our effort.
The question is often asked about what pattern to use for a baby quilt and my response is always "what ever pattern you want". It is the fabric that says baby, child or theme. Since I make my quilts with the intention that they will be used for years, I choose not to make they too "baby" but more juvenile or fabric that is interesting to look at and that is soothing. My choice, my way, your choice, your way is always the guideline that works best.