1. Use of the WHO Growth Standards in the United States APHA November 5, 2007
Laurence M. Grummer-Strawn
Nutrition Branch
Division of Nutrition, Physical Activity, and Obesity

2. Background NCHS 1977 growth reference used worldwide until 2000
CDC 2000 growth reference currently in use across the U.S. for children aged years
April 2006, WHO released a new international growth standard for children aged years

3. Recommendations for the U.S.
Expert panel was convened June 29-30, 2006
Sponsored by CDC/NIH/AAP
Considered
Rationale for standard vs. reference
Use of international data for the U.S.
Implications for breastfed as well as formula-fed infants
Methods in construction of both curves
Statistical comparisons between the curves
Practicalities of using multiple charts

4. Rationale for standard vs. reference
Because clinicians make decisions on health of the child, standard may be more appropriate
Qualitative research has shown that clinicians understand the use of a standard
But communication to parents about what a given percentile means would be difficult

5. Use of international data for the U.S.
Data on children from India, Ghana, Norway, Brazil & Oman
Data show that difference across countries are small
U.S. is a mixture of many nationalities
But communication to parents about why these comparisons are appropriate may be difficult

6. Implications for breastfed as well as formula-fed infants
Concerns over using breastfeeding standard for formula-fed children
But others concerned over using formula-fed reference for breastfed children (2/3 in CDC charts not breastfed beyond 3 months.)
AAP has said that breastfed child is the norm
Intake of breastfed child is used for setting DRIs
Separate charts for breast- and formula-fed babies are impractical

7. Methods in construction of both curves
CDC 2000 growth reference
Describes growth in the U.S. in the 1970s and 1980s
Based on nationally representative data
VLBW infants excluded
4 references:
Weight-for-age 0-20 yrs
Length-for-age 0-3 yrs/Stature-for-age 2-20 yrs
Weight-for-length & weight-for-stature 0-6 yrs
BMI-for-age 2-20 yrs

8. Key differences (Birth-2 yrs)
WHO
Longitudinal data
Feeding requirements
Exclusive/predominant breastfeeding > 4 months
Complementary feeding by 6 months
Continued breastfeeding > 12 months
Frequent data collection
biweekly 0-8 weeks
Monthly 2-12 months
Bimonthly months
18,973 observations
CDC
Cross-sectional data
No feeding requirements
~50% ever breastfed
~33% breastfeeding at 3 months
No data between birth and 3 months
mathematical models used
4,697 observations

9. Smaller differences at 2-5 yrs
WHO
Cross-sectional data
Feeding requirements
Breastfed at least 3 months
Stop at age 5
Overweight children (above +2SD) excluded
6,669 observations
CDC
Cross-sectional data
No feeding requirements
Continuous with curves up to age 20
No data exclusions
9,894 observations

10. Statistical comparisons between the curves
More infants will “fall off” WHO weight-for-age charts up to age 3 months but fewer will “fall off” from 3-18 months
Fewer infants would be below 5th percentile on WHO weight-for-age charts
More infants would be above 95th percentile on WHO weight-for-length or BMI-for-age charts
More infants would be below 5th percentile on WHO length-for-age charts

11. Cutoffs
WHO recommends cutoffs at -2 SD (2.3rd percentile) and +2SD (97.7th percentile)
In U.S., 5th and 95th percentiles more commonly used
Because WHO standard measured healthy children under optimal conditions, the more extreme cutoffs may be appropriate
Prevalence of stunting and overweight more similar using WHO cutoffs on WHO charts

12. Practicalities of using multiple charts
WHO curves only extend to age 5: Clinicians will need to use CDC charts for older children
If WHO curves adopted for 5 years, need to use 3 sets of curves:
0-2 years: WHO length-based
2-5 years: WHO stature-based
5-20 years: CDC stature-based
If WHO curves adopted for 2 years, need to use 2 sets of curves:
2-20 years: CDC stature-based

13. Next steps
AAP voted to support the WHO growth charts for birth to 24 months
CDC statement is in process of clearance
CDC developing supportive tools:
“Clinic-friendly” charts
Interactive web-based training modules