General information only. This Parent Resource summarizes WHO information about low birth weight and does not interpret an individual newborn’s condition.
How does WHO define low birth weight?
WHO defines low birth weight as weight at birth below 2500 grams.
Is low birth weight the same as being born preterm?
No. WHO explains that low birth weight can result from prematurity, restricted growth before birth, or both. Birth weight and gestational age therefore describe different aspects of a newborn.
Why is low birth weight monitored?
WHO uses low birth weight as a population-level indicator of maternal, newborn and nutrition conditions. It is included in global nutrition monitoring because it is associated with important short- and long-term health outcomes.
What does WHO’s current global target brief say?
WHO’s 2025 policy brief describes low birth weight as a continuing global public-health problem and extends international attention to reducing its prevalence through 2030.
A threshold does not determine an individual outcome. A newborn’s health cannot be inferred from birth weight alone.
References
- World Health Organization. Low birth weight.
- World Health Organization. Global nutrition targets 2030: low birth weight brief, 22 October 2025.