by Melissa Clark Vickers
September 21, 2010

Earlier this month, the Centers for Disease Control and Prevention (CDC) issued a statement recommending the World Health Organization (WHO) charts be used for all infants in the U.S. acknowledging that the growth of breastfed babies is the standard against which all infant growth should be compared.

Growth charts have long been a tool used by pediatricians and parents as a measure of health and well-being of children. Initially, charts were based on a population that was predominantly formula-fed, and because infants grow differently on formula than they do on human milk, decisions made based on “appropriate” growth were often skewed. Breastfed infants tend to gain weight faster in the first 3-4 months, but are generally leaner than their formula-fed counterparts by 12 months. In 2006, the World Health Organization (WHO) released a new set of growth charts for children 0 to 59 months, based not on how children do grow, but instead how they ought to grow.

The WHO standards were based on prospective data from a diverse population of babies who were given optimum nutrition (i.e. infants were exclusively breastfed for six months), after which age- and culturally-appropriate complementary foods in addition to human milk were provided. At the time, many countries were reluctant to implement these growth standards. As previously reported by baby gooroo, many were concerned whether the adoption of these new standards might have an adverse affect on breastfeeding rates. Among the concerns: Would these babies be given supplementary feedings? Would mothers be less likely to breastfeed exclusively or even continue breastfeeding? Would all mothers be given the high level of breastfeeding support that was required by mothers in the study population to establish and continue exclusive breastfeeding?

For years, no country adopted the WHO growth charts. In 2009, the UK was the first to implement the WHO child growth standards. And now, health care providers in the U.S. are being asked to implement the WHO growth standards for children up to 2 years old.

The CDC recommends that health care providers use WHO growth standards for children in the U.S. from age 0 to 2 years, and the CDC growth charts for children age 2 years and older. Although the WHO charts can be used for children up to age 5, the CDC recommends switching to their charts which can be used continuously for children aged 2-19 years, noting that for children 2-5 years old, the methods used to create the CDC charts are similar to those used for the WHO charts.

The CDC offers three reasons for why the WHO growth standards should be used for children under 2 years old in the U.S.:

1. The WHO standards assume breastfeeding is the norm for growth. Their charts are based on the growth of children who were predominantly breastfed for at least 4 months, and who were still breastfeeding at 12 months.
2. The WHO standards reflect a more accurate description of physiological growth during infancy. Previously, the CDC charts were used for infants, but because they were based on how typical U.S. children grew during a time when most were formula-fed, these “typical” patterns were not necessarily “ideal” growth patterns.
3. The WHO standards are based on a “high-quality study designed explicitly for creating growth charts.” CDC charts were based on a small sample size for the first 6 months of age, and had no weight data for the first 3 months. In contrast, the WHO standards used nearly 8,500 children from six countries (Brazil, Ghana, India, Norway, Oman, and the U.S.), and measured longitudinal length and weight data frequently.

A caution and a reminder
Growth charts are tool—one that should be used as part of a complete set of diagnostics to determine adequate and appropriate growth in children. A growth chart alone is not enough—family growth patterns and other indicators of good health and well-being are equally important. Also, charts are based on averages across a population. Unlike achieving a high score on a college entrance exam, being in the 95^th percentile on a growth chart is not inherently better than being in the 10^th percentile. The growth of each individual child should be measured against him or herself over time, with attention paid to changes in the growth rate, as well as overall development physically, mentally, and behaviorally.

The WHO growth charts

• Birth to 24 months: Boys Weight-for-length percentiles and Head circumference-for-age percentiles
  
• Birth to 24 months: Boys Length-for-age percentiles and Weight-for-age percentiles
  
• Birth to 24 months: Girls Weight-for-length percentiles and Head circumference-for-age percentiles
  
• Birth to 24 months: Girls Length-for-age percentiles and Weight-for-age percentiles

Editor’s Note—December 14, 2011
Researchers reviewed the velocity and trajectory of growth in the new WHO Growth Standards compared to the growth standards most commonly used in Australia. They found that the new growth standard is actually heavier in the first 6 months of life than the standard currently being used, and questioned whether adopting the new standard could cause more Australian babies to be supplemented due to poor growth. The researchers recommended conducting a randomized controlled trial before adopting the new growth standard to ensure that it will not adversely affect breastfeeding rates. Study results can be found in the December, 2011 issue of the Journal of Paediatrics and Child Health.