My Skinny Babe

Why baby sweaters are all too short and too wide for baby in question:


At 6 mos, my little bean pole checks in at a mere 13.5 lbs. I think average is about 17.5 lbs! This is a hard baby to knit for, especially since most of my baby patterns are boxy Debbie Bliss numbers. The question is, should I assume that she will continue to be this shape? I want to knit her some sweaters for next winter. Should I alter the patterns to account for the lack of baby chub and make them a bit more narrow in the chest? What do you knitters think?