title: Country-Specific vs. Common Birthweight-for-Gestational Age References to Identify Small for Gestational Age Infants Born at 24-28 weeks: An International Study.
abstract: Controversy exists as to whether birthweight-for-gestational age references used to classify infants as small for gestational age (SGA) should be country specific or based on an international (common) standard. We examined whether different birthweight-for-gestational age references affected the association of SGA with adverse outcomes among very preterm neonates.
  
  
  
  Singleton infants (n = 23 788) of 24(0) -28(6) weeks' gestational age in nine high-resource countries were classified as SGA (<10th centile) using common and country-specific references based on birthweight and estimated fetal weight (EFW). For each reference, the adjusted relative risk (aRR) for the association of SGA with composite outcome of mortality or major morbidity was estimated.
  
  
  
  The percentage of infants classified as SGA differed slightly for common compared with country specific for birthweight references [9.9% (95% CI 9.5, 10.2) vs. 11.1% (95% CI 10.7, 11.5)] and for EFW references [28.6% (95% CI 28.0, 29.2) vs. 24.6% (95% CI 24.1, 25.2)]. The association of SGA with the composite outcome was similar when using common or country-specific references for the total sample for birthweight [aRRs 1.47 (95% CI 1.43, 1.51) and 1.48 (95% CI 1.44, 1.53) respectively] and for EFW references [aRRs 1.35 (95% CI 1.31, 1.38) and 1.39 (95% CI 1.35, 1.43) respectively].
  
  
  
  Small for gestational age is associated with higher mortality and morbidity in infants born <29 weeks' gestational age. Although common and country-specific birthweight/EFW references identified slightly different proportions of SGA infants, the risk of the composite outcome was comparable.
authors.affiliation: Maternal-Infant Care Research Centre, Mount Sinai Hospital, Canadian Neonatal Network, Toronto, ON, Canada.
authors.forename: Lisa J
authors.initials: LJ
authors.lastname: Martin
authors.affiliation: Swedish Neonatal Quality Register, Department of Women's and Children's Health, Uppsala University, Uppsala, Sweden.
authors.forename: Gunnar
authors.initials: G
authors.lastname: Sjörs
authors.affiliation: Gertner Institute for Epidemiology and Health Policy Research, Sheba Medical Centre, Israel Neonatal Network, Tel Hashomer, Israel.
authors.forename: Brian
authors.initials: B
authors.lastname: Reichman
authors.affiliation: Australia and New Zealand Neonatal Network, Department of Paediatrics, University of Otago, Christchurch, New Zealand.
authors.forename: Brian A
authors.initials: BA
authors.lastname: Darlow
authors.affiliation: Department of Social Medicine, National Center for Child Health and Development, Neonatal Research Network Japan, Setagaya-ku, Tokyo, Japan.
authors.forename: Naho
authors.initials: N
authors.lastname: Morisaki
authors.affiliation: Neonatal Data Analysis Unit, Section of Neonatal Medicine, Department of Medicine, Imperial College London, UK Neonatal Collaborative, London, UK.
authors.forename: Neena
authors.initials: N
authors.lastname: Modi
authors.affiliation: Swiss Neonatal Network, Department of Neonatology, University Hospital Zurich, University of Zurich, Zurich, Switzerland.
authors.forename: Dirk
authors.initials: D
authors.lastname: Bassler
authors.affiliation: Maternal-Infant Care Research Centre, Mount Sinai Hospital, Canadian Neonatal Network, Toronto, ON, Canada.
authors.forename: Lucia
authors.initials: L
authors.lastname: Mirea
authors.affiliation: Swiss Neonatal Network, Department of Neonatology, University Hospital Zurich, University of Zurich, Zurich, Switzerland.
authors.forename: Mark
authors.initials: M
authors.lastname: Adams
authors.affiliation: Neonatal Research Network Japan, Maternal and Perinatal Center, Tokyo Women's Medical University, Shinjuku, Tokyo, Japan.
authors.forename: Satoshi
authors.initials: S
authors.lastname: Kusuda
authors.affiliation: Australian and New Zealand Neonatal Network, Royal Hospital for Women, National Perinatal Epidemiology and Statistic Unit, University of New South Wales, Randwick, NSW, Australia.
authors.forename: Kei
authors.initials: K
authors.lastname: Lui
authors.affiliation: Spanish Neonatal Network, Hospital Universitario de Salamanca, Valencia, Spain.
authors.forename: Laura San
authors.initials: LS
authors.lastname: Feliciano
authors.affiliation: Swedish Neonatal Quality Register, Department of Pediatrics/Neonatal Services, Umeå University Hospital, Umeå, Sweden.
authors.forename: Stellan
authors.initials: S
authors.lastname: Håkansson
authors.affiliation: Maternal-Infant Care Research Centre, Mount Sinai Hospital, Canadian Neonatal Network, Toronto, ON, Canada.
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Isayama
authors.affiliation: Neonatal Research Network Japan, Department of Health Policy, National Center for Child Health and Development, Setagaya-ku, Tokyo, Japan.
authors.forename: Rintaro
authors.initials: R
authors.lastname: Mori
authors.affiliation: Spanish Neonatal Network, Health Research Institute La Fe, Valencia, Spain.
authors.forename: Max
authors.initials: M
authors.lastname: Vento
authors.affiliation: Maternal-Infant Care Research Centre, Mount Sinai Hospital, Canadian Neonatal Network, Toronto, ON, Canada.
authors.forename: Shoo K
authors.initials: SK
authors.lastname: Lee
authors.affiliation: Maternal-Infant Care Research Centre, Mount Sinai Hospital, Canadian Neonatal Network, Toronto, ON, Canada.
authors.forename: Prakesh S
authors.initials: PS
authors.lastname: Shah
mesh_terms: D001315:Australia; D001724:Birth Weight; D002170:Canada; D005260:Female; D005602:France; D006801:Humans; D007231:Infant, Newborn; D007236:Infant, Small for Gestational Age; D007557:Israel / Q000453:epidemiology; D007564:Japan; D009520:New Zealand; D011247:Pregnancy; D012016:Reference Values; D013030:Spain; D013548:Sweden; D013557:Switzerland; D006113:United Kingdom
keywords: Infant, Extremely Premature; Infant, Small for Gestational Age; Neonatal outcomes