9. Plotting Measurements

Carefully calculate the child's age

Incorrect calculation of the age of the infant or child can be a significant source of error in plotting, and thus assessment of the growth of the child.

 EXAMPLE Jesse is an 8-month old female who weighs 7 kg (5th-10th percentile) and whose length is 65 cm (5th-10th percentile). If she was plotted incorrectly as a 6-month old infant, both her weight and length would lie between the 25th and 50th percentiles.

Would this error affect your clinical impression? If this was the only measure of this infant available, the clinical impression that both weight and length were between the 25th and 50th percentiles would be interpreted as appropriate growth for age. However, her actual growth between the 5th and 10th percentiles may be appropriate if this has been her growth pattern -- or it may warrant further investigation if it is a significant change from previous parameters.

 Chronological age is the most influential variable in rapidly growing children, so it is essential to know the exact age of the child for plotting all measurements. Age calculated from the birthdate and the date of each set of measurements or the stated age should be recorded.