EN head circumference velocity. Head circumference velocity. The velocity standards for head circumference are presented in 2- and 3-month increments from birth to 12 months, and 4- and 6-month increments from birth to 24 months.
Head circumference reflects brain size and is routinely measured up to 36 months. At birth, the brain is 25% of adult size, and head circumference averages 35 cm. Head circumference increases an average 1 cm/month during the first year; growth is more rapid in the first 8 months, and by 12 months, the brain has completed half its postnatal growth and is 75% of adult size.
Pediatricians measure an infant's head growth, or head circumference, along with height and weight on a regular basis to determine if the rate is age and gender appropriate. Although head circumference varies with each infant, pediatricians look for a trend in head growth from month to month.
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An infant whose head circumference measurements reflect either a slower or more rapid rate of growth is a red flag requiring a thorough evaluation. In order to appreciate the rate of weight, length, or head circumference growth, pediatricians commonly use a growth chart to keep serial records of such measurements.
Normal growth is the progression of changes in height, weight, and head circumference that are compatible with established standards for a given population. The progression of growth is interpreted within the context of the genetic potential for a particular child . Normal growth is a reflection of overall health and nutritional status.
Infants increase their head circumference by 12 centimeters during the first year of life as they start with an average of 35 centimeters and end up with an average of 47 centimeters. To remember the rates of increase at various months of the first year, we can use
The rate of brain growth is reflected in the head circumference, and any deviation from the normal trajectory, or greater than two standard deviations, is cause for concern. A head circumference smaller than two standard deviations defines microcephaly. A head circumference greater than two standard deviations defines macrocephaly.
There are separate growth charts for weight, height, and head circumference. These simply represent the average weight , height, or head circumference of a bunch of normal children.
Although many parents are preoccupied with where their child is on the growth charts and often worry if their child is small or near the bottom of the growth chart, it is your child's rate of growth that is the most important factor to consider when evaluating if your child is growing and developing normally.