A 2017 US Reference for Singleton Birth Weight Percentiles Using Obstetric Estimates of Gestation

• Published in: Pediatrics (Evanston) 2019-07, Vol.144 (1), p.1
• Main Authors: Aris, Izzuddin M, Kleinman, Ken P, Belfort, Mandy B, Kaimal, Anjali, Oken, Emily
• Format: Article
• Language: English
• Subjects: Birth size; Birth Weight; Births; Estimates; Female; Gestation; Gestational Age; Health aspects; Humans; Infant, Newborn; Male; Menstruation; Minority & ethnic groups; Natality; Obstetrics; Parity; Pediatrics; Pregnancy; Reference Values; United States
• ISSN: 0031-4005; 1098-4275
• DOI: 10.1542/peds.2019-0076

To provide an updated birth weight-for-gestational age (BW-for-GA) reference in the United States by using the most recent, nationally representative birth data with obstetric estimates of gestational age (GA). We abstracted 3 285 552 singleton births between 22 and 42 weeks' gestation with nonmissing race and/or ethnicity, infant sex, parity, birth weight, and obstetric estimate of GA from the 2017 US natality files. We used 2 techniques (nonlinear, resistant smoothing [4253H] and lambda-mu-sigma) to derive smoothed BW-for-GA curves and compared resulting BW-for-GA cut-points at the third, 10th, 90th, and 97th percentiles with US references from 1999 to 2009. The smoothed BW-for-GA curves from both techniques overlapped considerably with each other, with strong agreements seen between the 2 techniques (>99% agreement; κ-statistic >0.9) for BW-for-GA cut-points at the third, 10th, 90th, and 97th percentiles across all GAs. Cut-points from 2017 using the lambda-mu-sigma method captured 9.8% to 10.2% of births 90th percentiles and 2.6% to 3.3% of births below the third and above the 97th percentile across all GAs. However, cut-points from US references in 1999 and 2009 (when GA was based on last menstrual period) captured a much larger range of proportions of 2017 births at these thresholds, especially among preterm and postterm GA categories. We have provided an updated BW-for-GA reference in the United States using the most recent births with obstetric estimates of GA and information to calculate continuous measures of birth size that are sex or parity specific.