Understanding Growth Charts

During your child’s (many) check-ups during the first year after birth, it’s quite normal that your Naturopathic Doctor or Pediatrician will be filling out growth charts. Growth charts help to assess growth, nutritional status and well-being of your child. Understanding growth charts can be quite easy as they record weight, length, and head circumference. While there are 2 types of growth charts that doctors can use (WHO and CDC), WHO growth charts are the standard.

WHO created growth charts based on information from many children around the world who were primarily breastfed for at least 4 months. Measurements (of length and weight) were taken at many intervals to establish optimal growth patterns. CDC charts on the other hand, did not implement weight measurements when creating their chart especially between the 0-3 month range. Moreover, CDC charts took measurements from both breast and formula fed infants.

Breastfed infants grow more at the 2-3 month range and less rapid between 3-12 months (when compared to formula fed). In the 3-12 month interval, formula-fed infants grow more. This presents as an issue when a doctor is using a CDC chart to weight because at 5 months a formula fed child would be obtaining all his nutrients from mom, but not putting as much weight on when compared to a 5 month formula-fed baby. This may lead the doctor to want the mom (of the breast-fed baby) to begin solids or supplement with formula, so her baby can gain weight.

Growth Indicators

Length/height for age: reflects growth of length, which can be helpful when determining if a child is stunted due to prolonged malnutrition or chronic illness. While children can be tall for their age, it’s usually not an issue.

Weight for age: reflects body weight, to determine if a child is underweight. It it not used to assess if a child is overweight or obese. A body mass index (BMI) is calculated to determine if an individual is overweight or obese, usually over the age of 2.

Weight for length/height: reflects body weight in proportion to height, this determines if a child is wasting away due to food shortage or illness. However, it can be an indicator for the risk of becoming overweight or obese.

Head Circumference: indirectly reflects brain size and growth, and can help indicate brain health status. Keep in mind that most brain growth occurs before 2 years old.

Numbers

Growth charts assess the above indicators using one of two measurements: percentiles or z-scores. These numbers are used to determine where your child ‘ranks’ compared to others in his or her age range. Percentiles are commonly used by doctors as they are easier for everyone to understand. A percentile refers to where your child is compared to others (who’s data was used to determine the reference range). Anything below the 2nd and above the 98th are considered abnormal.

Once your child’s information has been plotted, you will be able to determine at which percentile they are at. At each visit, the measurements are compared to the previous set to assess growth pattern and if there is a need for further assessment.

Where your child is exactly on the percentile scale is less important than the range. Generally, they should be in the same range during each visit.  If they happen to drop 2 percentiles (ie. from 75 to 25, this would be a cause for concern). 

For children who were born prematurely (ie. 36 weeks and younger at gestation), their weight, length and head circumference is corrected for.  Weight, for example, is corrected for until 24 months, length for 40 months, and head circumference until 18 months.  

Things to keep in mind

Weight

• Newborns may lose 10% of their weight in the first few days of life (especially if breast fed)
• Weight at 6 months should be double its birth weight
• Weight at 12 months should triple its birth weight
• Weight at 24 months should quadruple birth weight
• Weight from 2 years old to puberty will be a steady increase

Length/Height

• Newborn length may not change much in the first few weeks, they may measure longer though as they become more stretched out
• By 3 years old, height should be measured with the child standing
• Height should increase by 30% by 5 months
• Height should increase by 50% by 1 year
• Height should be double by 5 years old

REFERENCES:

• CDC. Use and Interpretation of the WHO and CDC Growth Charts for Children from Birth to 20 Years in the United States.
• WHO. Interpreting Growth Indicators. 2008.
• Youfa Wang and Hsin-Jen Chen. Use of Percentiles and Z -Scores in Anthropometry. Handbook of Anthropometry. 2012.