what size blocks are you using?
6 1/2" blocks in a 5x7 block setting is 30x42 before borders
adding a 4" border makes it a 37x49 nice size baby quilt
I personally like to make them square and a little larger than standard baby size so they can use them as toddlers.
so go with the 7x7 block setting
I like an approx 60x60" finished
Mom and baby can both snuggle under it!