A newborn at term is about 20 inches in length, although the norm ranges between 18 and 22 inches. The average newborn weight ranges from 5 pounds 8 ounces to 8 pounds 13 ounces, according to KidsHealth.
An infant loses up to 10 percent of his birthweight in the days following his birth. He regains it quickly, returning to his birthweight in approximately seven days. Breastfed infants initially lose more weight than their bottle-fed counterparts and gain it back more slowly, according to an article in the ADC Fetal & Neonatal Edition. However, infants who are exclusively breastfed grow at a faster rate after this point, until 6 months of age when the gap in growth patterns closes.
An infant grows rapidly during his first few months of life. In general, his weight increases by 4 to 7 ounces every week and he grows in length by about 1 inch every month. Growth does not follow a strictly linear pattern for infants. For example, growth spurts are common between 6 and 8 weeks of age, when an infant is substantially hungrier to accommodate the rapid growth.