Infant Period

Infancy describes the growth and development of the child from about the fourth week through the second year of life. The infant experiences rapid physical growth during this time. The birth weight doubles by the fifth month and triples by the end of the first year, and the infant gains about 2,300 to 2,700 gm (5 to 6 lb) per year for the next several years (Puckett & Black, 2004). The infant grows approximately 25 cm (10 in) by the end of the first year, an average of 13 cm (5 in) by the end of the second year, and 7 cm (3 in) the following year (Deiner, 1997). In addition to weight and length, head circumference is an important physical feature to measure at regular intervals. Changes in head circumference are important because they denote brain growth. During the first year of life, head circumference increases from 33 or 36 cm (13 or 14 in) at birth to about 43 or 46 cm (17 or 18 in), with most of this growth occurring during the early months of development. The circumferences of the chest and abdomen are about the same in the neonate, but during infancy the chest circumference becomes larger than that of the abdomen. Deciduous, or primary, teeth appear at about 6 to 8 months and continue to erupt until all 20 are in place by toddlerhood. The skeletal structure of the infant hardens, and the musculature increases in weight and density. Typically, African American children show more rapid skeletal growth than white children do, and the bones of females generally grow faster than those of males (Puckett & Black, 2004; Tanner, 1990).