Infant BMI & Growth Tracker (0-12 Months)
Specialized Weight-for-Length tracker for newborns and infants using WHO 0-24m standards. Reassures parents by tracking non-linear micro-growth spurts.
About
Standard BMI is statistically invalid for infants under 24 months. Instead, the World Health Organization (WHO) and pediatric endocrinologists rely on "Weight-for-Length" ratios. This metric is the gold standard for assessing nutritional status in infants, as it functions independently of age biases that can occur during rapid growth spurts.
This tool strictly adheres to WHO Child Growth Standards, which are based on the growth patterns of breastfed infants. It is designed to provide reassurance by normalizing the non-linear nature of infant development. A baby may gain weight rapidly one week and pause the next; this tracker contextualizes those micro-changes within the global standard for healthy development.
Formulas
The calculation uses the standard normal distribution function N applied to the LMS parameters for length x:
Where y is the weight, and M, L, S are parameters derived from the infant's length. This avoids the inaccuracy of calculating BMI (kg/m2) for bodies with high head-to-body ratios.
Reference Data
| Percentile | Interpretation | Parental Action |
|---|---|---|
| < 2nd | Low Weight-for-Length | Evaluate feeding frequency/latch (if breastfeeding). |
| 2nd to 98th | Normal Growth Range | Continue responsive feeding; growth is on track. |
| > 98th | High Weight-for-Length | Usually benign in breastfed infants; monitor trends. |