Your child's rapid and irregular physical development through childhood may surprise you. Great changes take place during his first three years, as 75 percent of his brain growth happens in that short time, according to Growing Child. His motor development improves steadily until he reaches 12 years old, and a final rush of growth at puberty sees him turning into an adult.
Infant Development
Most babies weigh from 6 pounds to over 9 pounds, and measure 19 to 21 inches, according to KidsHealth. Your newborn does not control her own movements, but has a collection of reflexes that disappear within six months. She sucks hard and turns to a food source. If she hears a loud noise, she shows a startle reflex, throwing out her arms and legs then curling them in again. She grasps hold of anything that touches her palm.
The First Year
During his first year, your baby triples his birth weight and grows another 10 inches. He sits by 6 months and learns to move around, first by rolling, then crawling or shuffling. He pulls himself up on the furniture and takes his first steps at around 12 months, according to the U.S. Centers for Disease Control and Prevention. He starts to reach out and take hold of objects around the middle of his first year. Then, using both hands, he bangs objects together and finds he can put them in and out of containers.
Between 1 and 3 Years
In her second year, your toddler may gain between 3 and 5 pounds, and by her second birthday she will stand about 34 inches tall. She looks more muscular, losing some of her rounded softness as she gets active: running, jumping and kicking while her growth rate slows down a little. Before she is 3 years old, she will grow only another 2 to 3 inches. She climbs well, and learns to hold a pencil in a writing position while she makes up-and-down and circular lines on paper.
Your Preschool Child
A preschool child of 3 to 5 years gains greater large-muscle control, according to ED.gov. He learns to catch a ball, to run and jump fast and skilfully and to hop. He fizzes with energy, and may be aggressive as he plays. At the same time, he can control his smaller muscles, improving his scribbles and drawings as his pencil skills mature. Height and weight vary between individual children now, depending on each child's genetic inheritance from tall or short, large or small parents.
Middle Childhood
In middle childhood, between 6 and 12 years, your child adds about 2 to 3 inches in height and 5 pounds in weight each year. Worldwide, there can be up to 9 inches difference between individual children at 8 years old, according to the University of Kansas Department of Psychology, writing on their website. At this age, children move very flexibly, as their ligaments are not yet firmly attached to their bones. By the time she reaches 12 years of age, your child's first teeth have all been replaced by permanent teeth. Now, her motor development slows. During her middle years, she has a 25 percent chance of short-sightedness or myopia.
Teen Development
The final, dramatic stage in your child's physical development takes place between 12 and 18 years. During this stage of teen development, she becomes physically mature. Your daughter will develop breasts and pubic hair and begin her menstrual periods. Your son's testicles and scrotum, having begun enlarging when he was only 8 years old, reach their full size when he is 17, according to MedLine Plus. His voice changes, and he has a final growth spurt. Your child is now an adult.
