Some tots walk sooner, while others talk earlier.

Major Milestones in the Biological Development of Children

by Karen Hellesvig-Gaskell

Getting bigger, taking a first step, saying a first word (mama of course!) and understanding what you say are examples of major milestones in the biological development of toddlers and preschoolers. While it may be tempting to play an internal game called "the mom whose tot develops the most skills first wins," this would not only be a bit immature but unfair. Major developmental milestones can vary considerably from child to child.

1. Physical Growth

Physical growth takes place in two phases: birth to 2 years and 2 years until puberty. Infants grow approximately 10 inches during the first year, according to the Merck Manual. A preschooler has doubled her birth length or height by age 5. For example, if your daughter was 19 inches long at birth, she would stand 38 inches or 3 feet 2 inches tall when she starts kindergarten. Boys reach half their adult height at 24 months, while it takes only 19 months for girls to do so. By age 2, your toddler probably weighs four times more than the day he was born. If he came into this world a healthy 8 lbs, chances are the number 32 or thereabouts will appear when he steps on a scale. From age 2 until puberty you can expect your child to gain about 4 1/2 lbs per year.

2. 12 to 18 Months

A 12- to 18 month-old will go from taking a few cautious steps while holding onto a table for dear life to confidently walking along. She may even run and walk up and down stairs as the 18-month mark approaches. A 12-month-old likes to bang, shake and throw things in the name of exploration. He can say a few words and drink from a cup. A sippy cup is probably best unless you enjoy cleaning up spills! A tot’s vocabulary will grow over the next 6 months, as will her imagination and emotions. Pretending to feed a doll or stuffed animal and the first of many temper tantrums may occur.

3. 2 to 3 Years

Two- to 3-year-old tots are mobile machines. During this incredible year, a young child runs like a champ, rides a tricycle, and climbs playground ladders and stairs with ease. He can also say sentences of at least two to three words and count up to 10. Bragging rights in the third year of life include turning single book pages and dressing himself when it requires little effort such as putting on sweat pants and a T shirt, building towers at least six blocks high and completing three- to four-piece puzzles. Potty training typically takes place during this stage of development. About half of children in this age group are trained and will give you a heads up when they need to use the bathroom. By the time your toddler is 2 1/2, all his baby teeth should have erupted.

4. 4 to 5 Years

A 4-year-old is a cooperative playmate and would rather hang out with other kids than go solo. That's quite a change from the preference for solitary play at age 2 or 3. As a preschooler gets closer to kindergarten age, pleasing and being like her friends will carry more weight. An older preschooler has nailed some basic grammar skills like using "she" and "he" correctly. He speaks clearly, uses full sentences, and can say his first and last name. Motor skills have advanced to hopping, skipping and performing a smooth somersault. Four to 5-year-olds are old pros at using a spoon and fork, and some may even take a stab at using a table knife.

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