Study develops updated national birth weight reference

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BOSTON, MA – A new paper provides an updated national birth weight reference for the United States using the most recent, nationally representative birth data. The study, “A 2017 US reference for singleton birth weight percentiles using obstetric estimates of gestation,” led by the Harvard Pilgrim Health Care Institute, appears in the June 14 issue of Pediatrics.

Fetal growth, typically measured as birth weight-for-gestational-age is an important clinical indicator of morbidity, survival, and long-term health outcomes in children and their mothers. Previous birth weight-for-gestational-age references may not reflect the current socio-demographic composition of the U.S. and rely on less accurate estimates of gestational age. Investigators conducted this project to create an updated reference for clinicians and researchers using the most recent, nationally representative data on birth weight and more reliable obstetric estimates of gestational age.

The study team used data on over 3 million live births from the 2017 U.S. Natality files, a database of U.S. birth certificates publicly available from the National Vital Statistics System of the National Center for Health Statistics. Investigators used their analyses to provide a simple, easy to use online tool for both researchers and clinicians to calculate measures of birth size.

“Given the concerns regarding the validity of previous birth weight references based on maternal reports of last menstrual period, the need for an obstetric estimate-based reference has become increasingly appreciated. This updated reference will allow researchers and clinicians to weigh its appropriateness against their specific needs,” said lead author Izzuddin Aris, PhD, Research Fellow in the Department of Population Medicine at the Harvard Pilgrim Health Care Institute and Harvard Medical School. “We expect clinicians to be able to use the percentile thresholds from this updated reference to identify at-risk infants who may have had restricted or excessive fetal growth. Researchers may also use this reference to derive continuous measures of birth size for studies examining predictors of fetal growth or associations of fetal growth with later health outcomes.”

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About Harvard Pilgrim Health Care Institute’s Department of Population Medicine

The Harvard Pilgrim Health Care Institute’s Department of Population Medicine is a unique collaboration between Harvard Pilgrim Health Care and Harvard Medical School. Created in 1992, it is the only appointing medical school department in the United States based in a health plan. The Institute focuses on improving health care delivery and population health through innovative research and teaching.

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