it is up to you- is the baby in a cold climate? is there a lot of seams on the top (they will show through- feel through a plain flannel back without batting) I've made many, many flannel backed quilts baby right on up to kings- I've only left the batting out of one- it's ok- but doesn't have the soft, cozy feel of a quilt - it's flat and very light weight--if that's what you are going for then by all means- do it that way.