title: Birth weight in live births and stillbirths.
abstract: OBJECTIVE
  To establish a normal range of birth weights for gestational age at delivery and to compare the proportion of live births and stillbirths that are classified as small-for-gestational age (SGA) according to our normal range vs that of the INTERGROWTH-21ststandard.
  
  
  METHODS
  The study population comprised 113 019 live births and 437 (0.4%) stillbirths. The inclusion criterion for establishing a normal range of birth weights for gestational age was the live birth of a phenotypically normal neonate ≥ 24 weeks' gestation and the exclusion criteria were smoking and prepregnancy hypertension, diabetes mellitus, systemic lupus erythematosus or antiphospholipid syndrome, pre-eclampsia, gestational hypertension, gestational diabetes mellitus or iatrogenic preterm birth for fetal growth restriction in the current pregnancy. Inclusion criteria were met by 92 018 live births. The proportions of live births and stillbirths with birth weights < 5thand < 10thpercentiles of our normal range and those according to the INTERGROWTH-21ststandard were determined and compared by the chi-square test and McNemar test.
  
  
  RESULTS
  The proportions of live births and stillbirths with a birth weight < 5thpercentile according to our standard were significantly higher than and discordant with the proportion according to the INTERGROWTH-21ststandard (live birth: 5.6% vs 3.4%; stillbirth: 37.2% vs 22.7%). Similarly, the proportion of live births and stillbirths with a birth weight < 10thpercentile according to our standard were significantly higher than and discordant with those according to the INTERGROWTH-21ststandard (live birth: 11.2% vs 6.9%; stillbirth: 44.3% vs 32.6%).
  
  
  CONCLUSIONS
  The INTERGROWTH-21ststandard underestimates the proportion of SGA live births and stillbirths in our population. Copyright © 2016 ISUOG. Published by John Wiley & Sons Ltd.
authors.affiliation: Harris Birthright Research Centre for Fetal Medicine, King's College Hospital, London, UK.|Department of Obstetrics and Gynaecology, The Chinese University of Hong Kong, Hong Kong.
authors.forename: L C Y
authors.initials: LC
authors.lastname: Poon
authors.affiliation: Harris Birthright Research Centre for Fetal Medicine, King's College Hospital, London, UK.
authors.forename: M Y
authors.initials: MY
authors.lastname: Tan
authors.affiliation: Harris Birthright Research Centre for Fetal Medicine, King's College Hospital, London, UK.
authors.forename: G
authors.initials: G
authors.lastname: Yerlikaya
authors.affiliation: Harris Birthright Research Centre for Fetal Medicine, King's College Hospital, London, UK.
authors.forename: A
authors.initials: A
authors.lastname: Syngelaki
authors.affiliation: Harris Birthright Research Centre for Fetal Medicine, King's College Hospital, London, UK.
authors.forename: K H
authors.initials: KH
authors.lastname: Nicolaides
mesh_terms: D001724:Birth Weight; D005260:Female; D005865:Gestational Age; D006801:Humans; D007231:Infant, Newborn; D007236:Infant, Small for Gestational Age; D050498:Live Birth / Q000453:epidemiology* / Q000208:ethnology; D011247:Pregnancy; D050497:Stillbirth / Q000453:epidemiology* / Q000208:ethnology; D006113:United Kingdom / Q000208:ethnology
keywords: INTERGROWTH‐21st standard; birth‐weight percentiles; normal range; pyramid of antenatal care; small‐for‐gestational age; stillbirth