It is important for parents to be knowledgeable about normal growth. The average birth weight for a full term infant is 7 lbs 4 oz or 3.3 kilograms (kg). Probably as a result of loss of excess fluid, weight drops up to 10% in the first week of life; birth weight should be regained by two weeks of age. Breastfed infants tend to regain birth weight a little later than bottle fed infants.
On average, infants gain about 2 lbs or 1 kg per month for the first 3 months, 1 lb or ½ kg per month from 3-6 months of age, ¾ lbs or 1/3 kg per month from 6-9 months of age and ½ lb or ¼ kg per month from 9-12 months of age. Full term infants double their birth weight by 4 months of age and triple it by 12 months of age.
The average head circumference at birth is 13.5 in or 35 cm and increases rapidly to 18.5 in or 47 cm by 1 year of age; the rate of growth then slows down reaching an average of 21.5 in or 55 cm by 6 years of age.