Every parent expects their child to receive routine childhood vaccinations during well-baby check-ups. An equally important component of these visits is the monitoring of your child’s growth and development. Your pediatrician or family physician will measure your child’s growth parameters: height (length), weight and head circumference. She will plot them on standard growth charts to determine how your child’s growth compares to other children and, more important, whether he or she is following a consistent and healthy pattern of growth over time.

The higher your child’s percentile on the growth chart, the bigger he or she is compared to others of the same age. For example, if your 6-month–old baby is in the 60th percentile for weight and 70th percentile for height, it means that he’s heavier than 60 percent of 6-month-old babies and lighter than 40 percent, and taller than 70 percent of babies his age and shorter than 30 percent. A higher percentile ranking doesn’t indicate better health nor does a lower one indicate poor health. It just shows where your child is, compared to the growth of others his or her age.

Many factors affect the growth of your child including diet and activity, family history of growth (especially height of the parents) and overall health. Two of my five exceptionally charming grandchildren are likely to be taller than average (as children and adults) as their parents are both taller than average.

Growth normally can be erratic, and children sometimes go through spurts of rapid growth alternated with periods of slower growth. When should you worry about your child’s growth? It’s concerning if a pattern of growth changes significantly. For example, if your child has been in the 60th percentile for three years and then slows to the fifth to 10th percentile, you and your doctor will want to determine why the pattern has changed. Remember that patterns and trends of growth are more important than any individual plot on a growth chart.

Why measure head circumference? If your baby’s head growth is less than average, your doctor will make sure his other development—speech, motor, social, fine motor—is normal. If it’s faster and larger than average, there are other very rare problems to look for.

Do birth weight and length matter? Probably less than you think. Birth weight can be affected by many factors, including blood flow across the placenta and gestational age. A baby born at 34 weeks of gestation will be smaller than if he waited in the uterus another four to six weeks, but he’ll catch up. The stature of parents is the best indicator of eventual adult height.

Dr. Joseph Kahn is president of Mercy Kids (mercykids.org), an expansive network of pediatric care dedicated to meeting the needs of every child, every day.

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