Child growth → Weight-for-length

"Length" refers to measurement lying down, used for children under 2. "Height" is measured standing, for ages 2+. Recumbent length is about 0.7 cm longer than standing height because the spine compresses slightly when vertical.

These boundaries, not 5th and 95th, define normal on WHO charts. About 3% of healthy children naturally fall below the 3rd or above the 97th. Being outside this range prompts evaluation but doesn't automatically indicate a problem.

Babies born small or large often adjust toward their genetic potential in the first year. A small baby with tall parents may "catch up" to higher percentiles. A large baby with smaller parents may "catch down." This movement is expected and healthy.

Weight-for-length is preferred for children under 2 because it doesn't require knowing exact age and because infant body proportions change so rapidly. After age 2, BMI-for-age becomes standard.

3rd to 97th percentile is considered normal. Most healthy babies fall within this range. Below 3rd may indicate underweight; above 97th may suggest overweight. But some babies are naturally at the extremes due to genetics.

Not necessarily. Single drops are common and often reflect normal growth variability or measurement differences. What concerns pediatricians is sustained downward trends across multiple visits. If your baby seems healthy and is feeding well, a single percentile drop usually isn't alarming.

Yes. Breastfed babies typically gain weight faster initially, then slow compared to formula-fed babies. Since WHO charts are based on breastfed infants, formula-fed babies may appear to track higher in later infancy. Both patterns can be healthy.