CT: 11 Determining BMI & Plotting Infant/Child Growth Measurements

Effective Date: 07/92 Downloads: PDF Version    Revised Date: 05/10
   

Policy

When determining program eligibility, each applicant or participant’s growth measurements shall be plotted on the appropriate growth chart or prenatal grid.

Procedure

I.   Calculating Chronological Age

Before a growth measurement can be plotted, it is necessary to calculate the infant or child’s exact age in years, months, and days since birth. If the chronological age is not correctly determined, an error in plotting can occur.

 

Example:

Date of birth:               February 26, 1990

Today’s date:              January   11, 1992

Step 1: Rewrite the date of today’s measurement as

92(year)          1(month)         11(day)

Step 2: Rewrite the infant or child’s date of birth as:

90(year)          2(month)         26(day)

Step 3:             In order to subtract you will need to borrow months and days.

CT-11

Step 4:             Record age as 22 months-15 days in the age box on the appropriate growth chart.

             

II.    Gestational Age Adjustment for Premature Infants up to 2 years of Age                               

For WIC nutrition risk determination, adjusted gestational age should be calculated for all premature infants for the first 2 years of life. Prematurity is defined as infants born less than or equal to 37 weeks gestation.

  • Document the infant’s gestational age in weeks. (Can be self-reported, or referral information from the medical provider may be used).
  • Subtract the infant’s gestational age in weeks from 40 weeks (gestational age of full-term infant) to determine the adjustment for prematurity in weeks.
  • Subtract the adjustment for prematurity in weeks from the infant’s chronological postnatal age in weeks to determine the child’s gestational age.

 

EXAMPLE:  

Infant was born prematurely on March 19, 2010. His gestational age at birth was determined to be 30 weeks.  At the time of June 11, 2010 clinic visit, his chronological age is 12 weeks. Below you can see the calculations to adjustment of gestational age:

 

  • 30 = gestational age in weeks at birth
  • 40 – 30 = 10 weeks adjusted for prematurity
  • 12 – 10 = 2 weeks (adjusted gestational age)

 

The infant’s age would be plotted on a growth chart as a 2 week old infant.

Preterm infants that have not reached the equivalent age of 40 weeks gestation cannot be plotted on the 2000 CDC Growth Chart. Document as “unable to plot”

 

III.        Calculating BMI

BMI is calculated by using weight and stature measurements to compare a child’s weight relative to stature with other children of the same age and gender. To calculate BMI the following can be utilized:

 

A.  Using a calculator, determine BMI with the following calculation;

BMI = Weight (lb) ¸ Stature (in) ¸ Stature (in) ´ 703

Or

BMI = Weight (kg) ¸ Stature (cm) ¸ Stature (cm) ´ 10,000

 

Example:

English:     Child’s weight 37 lbs and 4 oz = 37.25 (16 ounces = 1lb so 4 oz/16oz= 0.25)

     Child’s height 41 ½ inches = 41.5 in. (37.25 lbs/ 41.5 in/ 41.5 in) x 703 = 15.2

Metric:       Child’s weight 16.9 kg. Child’s height 105.4 cm.

    (16.9 kg / 105.4 cm/ 105.4 cm) x 10,000 =15.2

B.  Look up in the Centers for Disease Control and Prevention (CDC) table for “Calculated Body Mass Index Values for Selected Heights and Weights for Ages 2 to 20 years”

C.  Obtain from current certification data entered into the WIC Program. Refer to the “WIC Computer Application Manual”

 

IV.    Plotting Measurements                           

Select the appropriate growth chart

To select the appropriate growth chart the following must be known

*  Sex of the infant or child

*  The infant or child’s chronological age

*  Type of measurement: stature or length, height, and head circumference

Use these charts when:    Use these charts when:   
 Infant birt-36 months (recumbent positions) Children 2-20 (standing height)
 * Weight – for – age  * Weight – for – age
 * Length – for – age  * Stature – for – age
 * Weight – for – length  * BMI – for – age
 * Head circumference – for – age

 

Record Data

  • Enter the child’s name and family number on both sides of the growth chart
  • Enter mother’s and father’s stature as reported
  • Enter date of birth, birth weight, length, and head circumference (birth to 36 months)

Current information obtained

  • Enter today’s date
  • Enter Infant/Child’s chronological age
  • Enter weight, length/stature, BMI, and head circumference (if appropriate)

 

Plotting Data 

  • Record and plot the data immediately
  • Use a hard or medium point pen (blue or black ink) and plot the charts on a firm surface
  • Use an Accuplot to assure accuracy with plotting
  • Always plot all grids for each infant or child

Plotting Length or Height-for-Age/Weight-for-Age

On the horizontal axis, locate the infant or child’s age. On the vertical axis, locate the infant or child’s length or height in inches/ weight in pounds and ounces. Using an Accuplot, make a dot exactly where the two values intersect.

Plotting Weight-for- Length  

On the horizontal axis, locate the infant or child’s weight in pounds and ounces.

On the vertical axis, locate the infant or child’s recumbent length in inches.

Using the Accuplot, locate the point where these two values intersect. Make a dot exactly at that point.

Plotting BMI-for-Age (≥ 24 months of age only) 

On the horizontal axis, locate the child’s age. On the vertical axis, locate the calculated BMI value. Using the Accuplot, locate the point where these two values intersect. Make a dot exactly at that point.

Plotting Head Circumference 

On the horizontal axis, locate the infant’s age. On the vertical axis, locate the infant’s head circumference in inches. Using the Accuplot, locate the point where these two values intersect. Make a dot exactly at that point.