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. 2017 Feb;21(2):283-289.
doi: 10.1007/s10995-016-2131-9.

2500-g Low Birth Weight Cutoff: History and Implications for Future Research and Policy

Free PMC article

2500-g Low Birth Weight Cutoff: History and Implications for Future Research and Policy

Michelle M Hughes et al. Matern Child Health J. .
Free PMC article


Purpose To research the origins of the 2500 g cutoff for low birth weight and the evolution of indicators to identify newborns at high mortality risk. Description Early research concluded "prematurity", measured mainly through birth weight, was responsible for increased health risks. The World Health Organization's original prematurity definition was birth weight ≤2500 g. 1960s research clarified the difference between gestational age and birth weight leading to questions of the causal role of birth weight for health outcomes. Focus turned to two etiologies of low birth weight, preterm births and intrauterine growth restriction, which were both causally associated with morbidity and mortality but through different pathways; a standard cutoff based on gestational age or customized cutoff was debated. Assessment While low birth weight can be due to preterm or intrauterine growth restriction (or both), the historic 2500 g cutoff remains the standard by which the majority of policy makers define low birth weight and use it to predict perinatal and infant adverse outcomes. Conclusion Current efforts to refocus research on preterm births and poor intrauterine growth are important to understanding the direct causes of mortality rather than low birth weight as a convenient surrogate. Such distinctions also allow researchers and practitioners to test and target interventions outcomes more effectively.

Keywords: Fetal growth; Intrauterine growth restriction; Low birth weight; Preterm birth; Small for gestational age.

Conflict of interest statement

The authors declare that they have no conflict of interest.

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    1. Adams MS, MacLean CJ, Niswander JD. Discrimination between deviant and ordinary low birth weight: American Indian infants. Growth. 1968;32(2):153–161. - PubMed
    1. Anderson NA, Lyon RA. Causes of prematurity. American Journal of Diseases of Children. 1939;58(3):586–594. doi: 10.1001/archpedi.1939.01990090140012. - DOI
    1. Ballantyne JW. The problem of the premature infant. British Medical Journal. 1902;1(2159):1196–1200. doi: 10.1136/bmj.1.2159.1196. - DOI - PMC - PubMed
    1. Battaglia FC, Frazier TM, Hellegers AE. Birth weight, gestational age, and pregnancy outcome, with special reference to high birth weight-low gestational age infant. Pediatrics. 1966;37(3):417–422. - PubMed
    1. Battaglia FC, Lubchenco LO. A practical classification of newborn infants by weight and gestational age. The Journal of Pediatrics. 1967;71(2):159–163. doi: 10.1016/S0022-3476(67)80066-0. - DOI - PubMed

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