Newborn sizes typically refer to the clothing and diaper sizes designed for infants from birth to about 3 months old. These sizes are often labeled as “newborn” or “0-3 months.” Newborn clothing is usually made to fit babies weighing up to 8-10 pounds and measuring around 20-21 inches in length. When shopping for newborn items, it's essential to consider that babies grow quickly. Some brands may have slightly different sizing, so checking the specific measurements on the label can help ensure a proper fit. Additionally, diapers come in various sizes, with newborn sizes accommodating babies up to 10 pounds.