title: Measuring placental transfusion for term births: weighing babies with cord intact.
abstract: OBJECTIVE
  To estimate the volume and duration of placental transfusion at term.
  
  
  METHODS
  Prospective observational study.
  
  
  METHODS
  Maternity unit in Bradford, UK.
  
  
  METHODS
  Twenty-six term births.
  
  
  METHODS
  Babies were weighed with umbilical cord intact using digital scales that record an average weight every 2 seconds. Placental transfusion was calculated from the change in weight between birth and either cord clamping or when weighing stopped. Start and end weights were estimated using both a B-spline and inspection of graphs. Weight was converted to volume, 1 ml of blood weighing 1.05 g.
  
  
  METHODS
  Volume and duration of placental transfusion.
  
  
  RESULTS
  Twenty-six babies were weighed. Start weights were difficult to determine because of artefacts in the data as the baby was placed on the scales and wrapped. The mean difference in weight was 116 g [95% confidence interval (CI), 72-160 g] using the B-spline and 87 g (95% CI, 64-110 g) using inspection. Converting this to the mean volume of placental transfusion gave 110 ml (95% CI, 69-152 ml) and 83 ml (95% CI, 61-106 ml), respectively. Placental transfusion was usually complete by 2 minutes, but sometimes continued for up to 5 minutes. Based on the B-spline, placental transfusion contributed 32 ml (95% CI, 30-33 ml) per kilogram of birth weight to blood volume, but 24 ml (95% CI, 19-32 ml) based on inspection. This equates to 40% (95% CI, 37-42%) and 30% (24-40%), respectively, of total potential blood volume.
  
  
  CONCLUSIONS
  Inspection of the graphs probably underestimates placental transfusion. For term infants, placental transfusion contributes between one-third and one-quarter of total potential blood volume at birth.
authors.affiliation: Bradford Institute for Health Research, Bradford Royal Infirmary, Bradford, UK. diane.farrar@bradfordhospitals.nhs.uk
authors.forename: D
authors.initials: D
authors.lastname: Farrar
authors.forename: R
authors.initials: R
authors.lastname: Airey
authors.forename: G R
authors.initials: GR
authors.lastname: Law
authors.forename: D
authors.initials: D
authors.lastname: Tuffnell
authors.forename: B
authors.initials: B
authors.lastname: Cattle
authors.forename: L
authors.initials: L
authors.lastname: Duley
mesh_terms: D001724:Birth Weight / Q000502:physiology*; D001810:Blood Volume / Q000502:physiology; D002585:Cesarean Section; D003250:Constriction; D036861:Delivery, Obstetric; D005260:Female; D006801:Humans; D007747:Labor Stage, First / Q000502:physiology; D010920:Placenta / Q000098:blood supply*; D011247:Pregnancy; D011446:Prospective Studies; D047929:Term Birth / Q000502:physiology*; D013997:Time Factors