Preemie     up to 7 lbs.   Newborn   0 - 6 Months   up to 13 lbs.   Small   6 - 12 Months   14 - 18 lbs.   Medium   12 - 18 Months   19 - 26 lbs.   Large   18 - 24 Months   27 - 34 lbs.

"Sleep and Play Baby Grow" Closed-Toe Long Johns - Click here to see items
Small = 3 Months
Medium = 6 Months
Large = 9 Months