CDC/WHO - Growth Charts

When the WHO growth curves were created, the differences in growth patterns of breastfed and formula-fed infants were considered.

-A healthy breastfed infant is the standard against which all other infants are compared. -All infants in the WHO sample were breastfed at least until aged 12 months and predominantly breastfed for at least 4 months. -Complementary foods were introduced at the mean age of 5.4 months. The breastfed infant is the reference or normative model against which alternative feeding methods are measured with regard to growth, healthy development, and all other short-term and long-term outcomes. This is consistent with U.S. dietary reference intakes, in which norms for infant intakes of most nutrients are determined on the basis of the composition of human milk and the average volume of human milk intake.

The CDC growth charts are a growth reference. They describe the growth of children in the United States. The CDC growth charts

-Are descriptive because they indicate how children grew in a particular place and time. -Indicate how children grew in the United States during approximately 30 years (1963 -1994). -Do not imply that the pattern of growth they represent is healthy. *Both the WHO growth standard and the 2000 CDC growth reference were developed to replace the 1977 National Center for Health Statistics (NCHS)/WHO growth reference.

The WHO growth charts represent growth standards that describe how healthy infants and young children should grow under optimal environmental and health conditions.The WHO growth charts

-Are prescriptive because they describe growth under optimal environmental conditions and included healthy infants who were well-fed according to international recommendations. -Were designed to be an international standard for infants and young children. -Provide a standard against which all infants should be compared. -Create an opportunity for clinicians to identify and address environmental conditions that might be negatively affecting growth.

The CDC growth reference charts are based on primarily formula-fed infants.

-Only about 50% of U.S. infants measured to create the CDC growth reference charts were ever breastfed. -By age 3 months, only 33% of U.S. infants were breastfed. In the United States most infants start to breastfeed. As a result, the CDC growth charts may not adequately reflect the current growth patterns of infants in the United States. They also do not reflect the growth pattern typically seen in breastfed infants.

WHO Multicenter Growth Reference Study (MGRS)

-The MGRS was conducted from 1997 to 2003 in six sites (Pelotas, Brazil; Accra, Ghana; Delhi, India; Oslo, Norway; Muscat, Oman; and Davis, California) to generate new growth curves to assess growth of infants and young children throughout the world. -A primary study hypothesis was that infants and young children have the potential to grow similarly, regardless of their race/ethnicity and place of birth, if they are breastfed, living in a healthy environment, and have adequate nutrition. -This hypothesis of similar growth was confirmed as the mean length measurements from birth up to 24 months in the 6 country sites were virtually identical.

The WHO standard charts use growth of the breastfed infant as the norm for growth.

-The WHO standards bring the tools used to assess growth and national guidelines that recommend breastfeeding as the optimal infant feeding method into agreement. -The WHO standards are based on high-quality data collected for children younger than aged 2 years -The WHO growth standard charts were created with longitudinal length and weight data measured at frequent intervals. -The CDC growth reference charts were based on cross-sectional length and weight data. However, weight data were not available for infants aged birth to 2 months, and the sample sizes were small for sex and age groups during the first 6 months of age.

Assessing Growth Using the WHO Growth Charts

-Use recommended protocols to measure the weight and recumbent length of the child accurately. Record the measurements correctly. -Accurately measuring and recording this information is critical for growth charts to be used as an effective screening tool. -Calculating age correctly is also critical for accurate growth determinations and interpretations. -Plot these measurements on the appropriate WHO growth chart. -Use the percentile lines on the chart to assess body size and growth and to monitor growth over time.

Use of the BMI-for-age growth chart is not recommended for children younger than age two years at this time.

-While the WHO growth standards include a BMI chart beginning at birth, the expert panel generally agreed that many questions about BMI during infancy remain unanswered so use of the BMI chart is not recommended for clinical use before age two years. -The BMI in infancy is based on recumbent length rather than stature and, to date, there has been little research on what BMI calculated from length means in infancy and on the consequences of high or low BMI in infancy.

After about 3 months of age, WHO growth charts show a slower rate of weight gain than the CDC growth charts.

A. True Beginning at around 3 months of age weight gain is generally lower for breastfed infants than for that of the formula-fed infant. Because the WHO growth charts were developed from a sample of breastfed infants, the growth curves follow the weight pattern of breastfed infants.

The growth patterns between breastfed and formula fed infants differ. Which statement accurately describes these differences:

B. Healthy breastfed infants typically gain weight slower than formula fed infants in the first year of life.

Development of the U.S. Recommendations to Use the WHO Growth Standards with Children Younger Than 2 Years of Age

Based on the comparison between the CDC growth reference and the WHO growth standards and input from the expert panel, CDC and AAP developed the following recommendations: -The WHO growth standard charts should be used for children younger than 2 years of age. -The CDC growth reference charts should be used for children aged 2 to 19 years. -The CDC growth reference charts are more suited for children 2 years and older because these charts can be used continuously up to age 20 years. The WHO released the international growth standards for young children ages birth to 5 years of age. However, for children ages 2 to 5 years, the WHO BMI-for-age charts offer little advantage over the CDC BMI-for-age charts for the assessment of child growth from 2 to 5 years of age as the data collection methodology was similar for the two charts.

The WHO growth charts represent growth standards that describe how healthy infants and young children should grow under optimal environmental and health conditions. To achieve this purpose, infants were excluded from the study sample used to create the growth curves if they were

Born to mothers who smoked during pregnancy or lactation. Breastfed <12 months. Introduced to complementary foods before 4 months of age. All of the above.

CDC Growth Reference

CDC growth reference charts were developed to represent all infants in the United States. Feeding criteria were not identified.

Differences in Methodology

Different approaches were used to construct the 2000 CDC and 2006 WHO growth charts for children from birth up to 2 years and include differences in the -Data sources. -Type and frequency of data collection. -Sample sizes. -Exclusion criteria. -Breastfeeding rates among infants in the sample. -Use of cross-sectional data to construct the CDC charts versus longitudinal data to construct the WHO growth charts.

Growth Monitoring

During this transition, caution should be used in interpreting any changes. -Growth measurements need to be used in conjunction with medical and family history if aberrant growth is identified. Growth monitoring is based on a series of measurements. -When assessing physical growth, it is critical to have a series of accurate measurements to establish an observed growth pattern. -A series of accurate measurements takes into consideration short- and long-term conditions and provides a context for individual measurements in interpretation. Thus, misinterpretation can be avoided based on a single plot on a different chart.

Infant Growth Patterns on the WHO and CDC Growth Charts

Growth patterns differ between breastfed and formula-fed infants. Beginning around 3 months of age weight gain is generally lower for breastfed infants than for that of the formula-fed infant. Linear growth generally follows a similar pattern for both breast- and formula-fed infants. -For the first 3 months of age, the WHO growth charts show a somewhat faster rate of weight gain than the CDC growth charts. -After about 3 months of age, WHO growth charts show a slower rate of growth than the CDC growth charts. --Because formula-fed infants tend to gain weight more rapidly after age 3 months, they may be more likely to cross upward in percentiles on the WHO growth charts, perhaps becoming classified as overweight. --Early recognition of a tendency toward overweight or obesity might appropriately trigger interventions to slow the rate of weight gain although no evidenced-based guidelines for treating overweight in infancy exist. ----Studies suggest that higher weight gain during infancy is associated with increased risk of obesity in childhood. Consequently, lower weight gain during the first two years of life may be beneficial to health in the long term.

Breastfeeding Advocacy

In 2006, the Centers for Disease Control and Prevention, the National Institutes of Health, and the American Academy of Pediatrics (AAP) convened an expert panel to review the scientific evidence and discuss the potential use of the new WHO growth charts in clinical settings in the United States. The expert panel agreed that breastfeeding is the optimal form of infant feeding. They also agreed that using the WHO growth charts for children aged birth to younger than 2 years, which are based on breastfed infants as the standard, helps to support current infant-feeding recommendations in the United States. The AAP recommends breastfeeding for at least 12 months, with exclusive breastfeeding for about 6 months.1 Other major health professional organizations agree with this recommendation for most infants in the United States. Examples of these organizations include the American Academy of Family Physicians,2 the American Dietetic Association,3 and the American Public Health Association AAP supports the position that breastfeeding ensures the best possible health, as well as the best developmental and psychosocial outcomes for the infant. Exclusive breastfeeding is sufficient to support optimal growth and development for about the first 6 months of life.

WHO Weight-for-Length Chart to the CDC BMI-for-Age Chart

Moving from the WHO weight-for-length chart to the CDC BMI-for-age chart may result in a change in a child's percentile classification because of -Changes from one indicator to another indicator. -Changes from a recumbent length measurement to a standing height measurement. -Changes to a different cutoff value and a different reference population. A child who is identified as being at a specific percentile when plotted on the WHO weight-for-length chart may "drop" to a lower percentile on the CDC BMI-for-age chart.For example, a 24-month-old boy weighing 24 pounds and 4 ounces with a length of 23.25 inches is plotted between the 25th and 50th percentiles on the WHO weight-for-length chart. When plotted on the CDC BMI-for-age chart, the same boy is plotted just above the 10th percentile. Both percentile classifications are within the healthy range.

WHO Growth Standards Represent Optimal Growth

The WHO growth standard charts are intended to reflect normal child growth under optimal environmental conditions. -Although many children in the United States do not experience the optimal environmental, behavioral, or health conditions specified in the WHO Multicenter Growth Reference Study, the WHO growth standard charts are intended for use with children younger than aged 24 months because they represent optimal growth

WHO Growth Standards

The WHO growth standard charts consider the effect of infant feeding on growth by using breastfeeding as the norm

Percentile Cutoff Values

The World Health Organization (WHO) recommends cutoff values of +2 standard deviations, which correspond to the 2.3rd and 97.7th percentiles, to define abnormal growth. -For the WHO growth charts modified by CDC, these cutoff values are labeled as the 2nd percentile and the 98th percentile. -Infants and children with a weight-for-length that is less than the 2nd percentile are classified as low weight-for-length. -Infants and children with a length-for-age that is less than the 2nd percentile are classified as having short stature. -Infants and children with a weight-for-length that is higher than the 98th percentile are classified as high weight-for-length.

WHO Percentile Cutoff Values Differ from Traditional CDC Cutoff Values

The cutoff values for the 2nd and 98th percentiles used in the WHO growth standard charts are different from those used in the CDC growth references chart. CDC uses the 5th and 95th percentiles. Different methods are used to create the WHO and CDC charts. Historically, CDC used the 5th percentile to define shortness and low weight-for-length, and the 95th percentile was used to define high weight-for-length. Using the WHO growth chart cutoff values indicates a change in clinical protocol. Theoretically, children in the WHO population would be expected to be healthy. Thus, more extreme cutoff values are more appropriate to define the extremes of growth of children rather than the values used in the CDC growth reference.

Breastfeeding as the Norm for Infant Feeding

The growth patterns of breastfed and formula-fed infants are different. For example, -Healthy breastfed infants typically put on weight more slowly than formula-fed infants in the first year of life. -Formula-fed infants typically gain weight more quickly after about 3 months of age. -Differences in weight patterns continue even after complimentary foods are introduced. Linear growth generally follows a similar pattern for both breastfed and formula-fed infants.

Interpreting Growth Indicators Using the WHO Growth Charts

There are differences in the prevalence of growth indicators when using the WHO growth charts compared to the CDC growth charts. A comparison of low length-for-age, weight-for-age and weight-for-length, and high weight-for-length in US children among infants and children up to 24 months of age using the 2006 WHO growth standard charts and the 2000 CDC growth reference charts (comparing the 2.3rd and 97.7th percentiles for the WHO growth charts and 5th and 95th percentiles for the CDC growth charts) shows that prevalence of nutritional status indicators are as follows. Low length-for-age: The prevalence of low-length-for-age is very similar (within 0.25 percentage points)1 on the WHO and the CDC growth charts. Low weight-for-age: In the first two years of life, the prevalence of low weight-for-age is generally lower on the WHO charts compared to the CDC 2000 charts except in the first 5 months of life when it is similar on both charts. This may be beneficial because over-diagnosis of low weight-for-age can result in unnecessary interventions and possibly damage the parent-child interaction. Children identified as having low weight-for-age on the WHO growth charts will be more likely to have a true weight deficiency that requires follow up. Low and high weight-for-length: The prevalence of low weight-for-length is about 3 percentage points lower on the WHO charts compared to the CDC charts. The prevalence of high weight-for-length is generally lower on the WHO charts compared to the CDC charts.

The CDC growth charts do not reflect a growth pattern typically seen in breastfed infants.

True

An advantage of using the WHO growth standard charts with all infants and children from birth up to aged 2 years is that

U.S. children were included in the WHO study sample and their growth is similar to other children in the sample. The WHO charts do not consider the effects of infant feeding on growth. The WHO charts are based on limited data for the first 6 months of life.

CDC Length and Weight for age chart

WHO Length-for-Age Chart Compared to the CDC Length-for-Age Chart In general, the WHO and the CDC length-for-age growth charts are somewhat similar. WHO Weight-for-Age Chart Compared to the CDC Weight-for-Age Chart -The WHO weight-for-age charts show a pattern of slower weight gain after about 3 months of age since they are based on the weights of breastfed infants. -When changing from the WHO-weight-for-age chart to the CDC weight-for-age chart at 2 years of age, the weight-for-age percentiles may change downward to a lower percentile. -For example, a weight of 26 ¾ pounds for a 24-month old boy is at about the 50th percentile on the WHO weight-for-age chart. The same weight on the CDC weight-for-age chart is between the 25th and the 50th percentile. Both percentile classifications are within the healthy range.

Features of the WHO Multicenter Growth Reference Study (MGRS)

WHO collaborated with the United Nations University Food and Nutrition Program, United Nations Children's Fund, CDC, several governments, and others to develop the WHO growth standards to replace the 1977 NCHS/WHO growth reference that had been used in the international community.

Transitioning from WHO to CDC Growth Charts at 2 Years of Age

When a child reaches age 24 months, health care providers need to switch from using the WHO growth standards charts to using the CDC growth reference charts for children ages 2 years up through 19 years. During the transition from one chart to another, children may experience a difference in classification because of a change from: -Recumbent length to standing height measurements. Note that the difference between recumbent length and stature in national survey data is approximately a 0.8 cm (¼ inch) difference. Standing height measures less than recumbent length. -Breastfed reference population to a primarily formula-fed reference population. -Weight-for-length chart to BMI-for-age chart. One set of cutoff values to another.

Which of the following statements are true:

When comparing the WHO growth chart cutpoint values of the 2nd and 98th percentiles to the CDC growth chart values of 5th and 95th percentile, the prevalence for low weight-for-length and high weight-for-length are very similar. The prevalence of high weight-for-length will be higher when using the WHO growth charts compared to the CDC growth charts. The prevalence of low weight-for-length will be lower when using the WHO growth charts compared to the CDC growth charts. Short stature prevalence will be lower when using the WHO growth charts.

Similarities in Methodology

While there were many differences in the design and methodology between the WHO and CDC chart development, similarities exist. -Growth curves for both charts were developed using an LMS methodology1-2 to describe both percentiles and z-scores (standard deviation units) although there were some differences in the smoothing techniques used to create the growth curves. -Data quality was tightly controlled in both studies with precise procedures for training and standardization of measurements using high quality anthropometry equipment. Optimal data entry and cleaning techniques were used.

The WHO growth charts are considered a standard against which all infants and young children should be compared because

a. The WHO growth standard curves are considered a standard against which all infants and young children should be compared because they describe how healthy infants and young children should grow.

The United States was not included as one of the study countries in which data were collected to construct the WHO growth standard charts.

false. Davis, California was included as a study site to generate the WHO growth curves. Other sites were included from Brazil, Ghana, India, Norway, and Oman

For children over 2 years of age, continued use of the 2000 CDC BMI-for-age charts is recommended.

true

The WHO growth standard charts were developed to describe optimal growth among infants and children.

true. The WHO growth standard charts describe how healthy infants and children grow under the 'best' health conditions such as being exclusively breastfed for at least 4 months and born to a mother who did not smoke during pregnancy or lactation.