This is my second simple joys purchase. I previously purchased a six pack of short-sleeved onesies which I loved so much that I had to come back and buy some long sleeved onesies for night time. I would say they fit as expected. My baby girl is seven months old and I bought her the 12 month size. The sleeves are a little long and she has some room to grow which is exactly what I wanted. Her other simple joys onesies are 6 to 9 months and they fit her perfectly for right now. She's about 18 pounds. I will definitely purchase this brand again. Soft cotton, cute prints, great value!