10 to 12 Baby Lounge are true size fit. For pieces that are close to the baby's skin, we increase their sizes every 3 months for the first year. This is because your baby grows so much during the first 12 months of their lives. For outerwear, we have a slightly different schedule. Their sizes increase every 6 months for the first year. The outerwear lasts longer. Starting from 2nd year, we only offer one size per year which is 2T.