title: Customized birthweight centiles predict SGA pregnancies with perinatal morbidity.
abstract: OBJECTIVE
  To determine the following: (1) the proportion of babies reclassified as small or appropriately grown using customized and population centiles; and (2) the relative risks of perinatal morbidity, including abnormal umbilical Doppler studies, in babies classified as small for gestational age (SGA) and appropriate for gestational age (non-SGA) using the two centile calculations.
  
  
  METHODS
  Cohort study in SGA and general hospital populations.
  
  
  METHODS
  National Women's Hospital, Auckland, NZ.
  
  
  METHODS
  A cohort of SGA pregnancies (n= 374) and a general obstetric population (n= 12,879).
  
  
  METHODS
  Pregnancy outcomes were compared between 'non-SGA both' (> or =10th% by population and customized centiles) and those who were 'SGA both' (<10th% by population and customized centiles), 'SGA customized only' (SGA by customized but non-SGA by population centiles) and 'SGA population only' (SGA by population but non-SGA by customized centiles).
  
  
  METHODS
  Maternal and newborn morbidity and perinatal death.
  
  
  RESULTS
  In the SGA cohort 271 (72%) babies were 'SGA both', 27 (7%) were 'SGA customized only', 32 (9%) were 'population SGA only' and 44 (12%) were 'non-SGA both'. In the general obstetric population 863 (6.7%) babies were 'SGA both', 445 (3.5%) were 'customized SGA only', 285 (2.2%) were 'population SGA only' and 11,286 (88%) were 'non-SGA both'. Perinatal death and newborn morbidity including nursery admission and long hospital stay were increased and comparable between 'SGA both' and 'customized SGA only' in both study populations. Newborn morbidity was low and comparable between 'population SGA only' and 'non-SGA both'. No perinatal deaths occurred in 'population SGA only' babies. Abnormal Doppler studies were more common in 'SGA both' or 'customized SGA only' but not in 'population SGA only' groups compared with 'non-SGA both'.
  
  
  CONCLUSIONS
  Customized birthweight centiles identified small babies at risk of morbidity and mortality. Use of customized centiles is likely to detect more babies at risk of perinatal morbidity and mortality than would be detected by population centiles.
authors.affiliation: Department of Obstetrics and Gynaecology, National Women's Hospital, University of Auckland, New Zealand.
authors.forename: Lesley M E
authors.initials: LM
authors.lastname: McCowan
authors.forename: Jane E
authors.initials: JE
authors.lastname: Harding
authors.forename: Alistair W
authors.initials: AW
authors.lastname: Stewart
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D001034:Apgar Score; D001724:Birth Weight / Q000502:physiology*; D001827:Body Height; D001835:Body Weight; D015331:Cohort Studies; D005260:Female; D005316:Fetal Distress; D005317:Fetal Growth Retardation / Q000209:etiology / Q000628:therapy; D006801:Humans; D007226:Infant Mortality; D007231:Infant, Newborn; D007236:Infant, Small for Gestational Age / Q000502:physiology*; D015931:Intensive Care, Neonatal / Q000706:statistics & numerical data; D007751:Labor, Induced / Q000706:statistics & numerical data; D007902:Length of Stay; D009035:Mothers / Q000706:statistics & numerical data; D011247:Pregnancy; D011256:Pregnancy Outcome; D012016:Reference Values; D018608:Ultrasonography, Doppler; D016216:Ultrasonography, Prenatal