• Serial weight and length / height measurements over time are needed for growth assessment
• Growth assessment involves looking at the overall tracking of weight and length / height on a growth chart
• Very few children grow along the same centile line from birth
• Weight and length /height 'tracking' along centile lines shows healthy growth

The best indicator of poor growth is weight and / or length tracking downwards on percentiles on the weight and / or length for age growth charts.

Other popular, but less reliable definitions in the past have included:

• weight dropping percentile lines on weight for age growth chart
• weight and length are more than 2 percentile lines apart on the weight and length for age growth charts
• Weight or length for age below the 3^rd centile

• Weight or length or BMI for age crossing centiles upwards
• In children over 2 years BMI above the 85^th centile on the BMI for age growth chart is considered overweight, BMI above the 95^th centile is considered obese

Chart 1: Weight is going up over time, but dropping on the percentile lines. This is a cause for concern.

Chart 1 (above)

Chart 2: Child has lost weight; this is a cause for concern

Chart 2 (above)

 
Chart 3: Weight value has not changed, but plotting shows decline on percentile chart. This is a cause for concern. 

Chart 3 (above)

Chart 4: Weight is going up quicker than expected for age. This is a cause for concern. 

Chart 4 (above)

Monitoring the growth of children with health issues such as prematurity, medical conditions known to alter growth, genetic disorders, developmental delays and disabilities requires additional considerations.  

Prematurity

Corrected age should be used until 2 years of age (or until the child 'catches' up or whichever is sooner). The optimal rate of weight gain or catch up growth is not known. There are concerns that rapid weight gain early in life may promote growth of excess fat cells and increase later risk of chronic illness 

Low birth weight

Low birth weight is defined as birth weight less than 2500g. Low birth weight infants born at, or near term are expected to track along a lower percentile on the weight for age growth charts. This includes infants with slow intra-uterine growth and infants from multiple births.  Low birth weight infants may 'catch up' over time to a higher percentile, or may follow their own line below the 3^rd percentile on the growth chart. Either way, weight and length should generally track  in proportion. Breastfeeding is encouraged for all infants irrespective of birth weight.  

Medical conditions / chromosomal disorders

Some conditions such as chromosomal disorders may change a child's growth potential. Specific charts have been developed for a range of different conditions, but are based on small numbers of children and are generally not recommended.

Further details on monitoring growth in children with special needs can be obtained at http://depts.washington.edu/growth/