During the first two years, the body enlarges more rapidly than at any time after birth. Normally, birth weight has doubled by five months of age, tripled by one year, and quadrupled at two years. Research has indicated that these height and weight gains occur in little growth spurts. Toddlers become more slender, a trend that continues into middle childhood. There are two patterns of growth that describe the maturing toddler.
Black babies are slightly ahead of Caucasian babies at all ages in height and weight.
Children of the same age differ in rate of physical growth, with girls growing more rapidly than boys at all ages. Girls are more resistant to harmful environmental influences, show fewer developmental problems, and have a lower infant and childhood mortality rate than boys. At birth, the brain is nearer to its adult size than any other physical structure. The human brain has 100-200 billion neurons, which store and transmit information. Since a given neuron may have hundreds of synapses, the number of synapses, or connections, in the brain is obviously over 200 billion.