The Centers for Disease Control and Prevention (CDC) publishes a series of growth charts that you can use to compare various body measurements for children by age and sex. One set of growth charts reflects specific information about weight distribution for infants from birth to 36 months in the United States, with one chart for boys and one for girls.
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According to the CDC, pediatric growth charts have been widely used in the U.S. since 1977, when the National Center for Health Statistics (NCHS) developed them as a tool to determine whether a child’s growth was adequate. The growth charts were updated in 2000 to reflect more comprehensive data gathered since the 1960s through the National Health and Nutrition Examination Survey (NHNES).
CDC growth charts for children through 36 months of age are graphs that depict your baby’s length and weight for age as percentiles. A percentile ranks the child according to the percentage of the population she equals or exceeds. For example, a 10-month-old girl who weighs 19.5 pounds is at the 50th percentile of weight for her age. This means that half of the female infants her age weigh the same or less, and half weigh the same or more.
The 2000 CDC growth charts include data from both formula-fed and breast-fed babies, according to the distribution of the population when the data was gathered, so they are considered appropriate for both groups of infants. However, the CDC notes, exclusively breast-fed babies tend to gain more weight in the first two to three months when compared with other infants, and they typically weigh less than formula-fed babies from 6 to 12 months of age. If you’re using these growth charts to compare your baby with other infants, it’s important to take these trends into account.
Kids Health emphasizes that growth charts are only guidelines and provide a single piece of data about your child’s health. If you find your baby is on the far end of the curve for weight by age, discuss the information with your doctor. She can discuss other factors such as genetics, environment, nutrition, hormones and health problems that influence an infant’s weight and height. The doctor will also review your baby’s position on the growth chart over time, looking for trends rather than a snapshot of one point in time.
The 2000 CDC growth charts include data from low birth-weight babies, but do not include very low birt- weight infants who weighed less than 3.3 pounds at birth. There are specialized growth charts for these tiny infants, as well as for those with Down syndrome.