title: Placental weight, digitally derived placental dimensions at term and their relationship to birth weight.
abstract: OBJECTIVE
  A few recent studies have investigated the relationship between birth weight and digitally derived placental dimensions, and no standardised methodology has been used. The aims of this study are to compare manually derived placental measurements with those derived digitally and to establish the relationship of birth weight to the placental weight and circumference.
  
  
  METHODS
  Three hundred fifty-one consecutive unselected women with singleton pregnancy delivering in a tertiary maternity unit at 37-42 weeks were recruited. Manual and digital placental axis measurements (using calibrated digital imaging and 'Image J' software) were obtained and the circumference derived. The relationship between the two methods was assessed using a Bland-Altman plot analysed. The relationship between z-scores of birth weight, placental weight and placental circumference was investigated.
  
  
  RESULTS
  Manually and digitally obtained placental long axis, short axis and circumference measurements show close correlation (r=0.70, 0.70 and 0.83, respectively). The z score of birth weight is significantly correlated with the z score of placental weight (r=0.59, p<0.001) and z score placental digital circumference (r=0.40, p<0.001). Birth weight:placental weight ratio is 7.20 and birth weight:placental circumference=64.57 g/cm.
  
  
  CONCLUSIONS
  There is close though not perfect agreement between the manual and digital placental measurements. Birth weight is strongly correlated with placental weight and circumference at term.
authors.affiliation: Division of Fetal Medicine, Addenbrookes Hospital, Cambridge University Hospitals NHS Foundation Trust, Cambridge, CB2 2QQ, UK.
authors.forename: Sangeeta
authors.initials: S
authors.lastname: Pathak
authors.forename: Flora
authors.initials: F
authors.lastname: Jessop
authors.forename: Liz
authors.initials: L
authors.lastname: Hook
authors.forename: Neil J
authors.initials: NJ
authors.lastname: Sebire
authors.forename: Christoph C
authors.initials: CC
authors.lastname: Lees
mesh_terms: D000328:Adult; D001724:Birth Weight; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D007231:Infant, Newborn; D010920:Placenta / Q000033:anatomy & histology* / Q000000981:diagnostic imaging*; D011247:Pregnancy; D011446:Prospective Studies; D014463:Ultrasonography