Once you have sewn the two seams together try the pants on your baby. If you have a little baby they should fit. But if you have a baby like mine who wears cloth diapers you will probably have to add some extra fabric from the rest of the sweater that you cut the sleeves off of. Cloth diapers definitely add some junk in the trunk! Those cute little skinny jeans for babies you find at the Gap aren’t going to fit over this butt! Vintage baby clothes are designed for big cloth diapers like my baby wears so they usually fit her.