title: Placental glucose transfer: a human in vivo study.
abstract: OBJECTIVE
  The placental transfer of nutrients is influenced by maternal metabolic state, placenta function and fetal demands. Human in vivo studies of this interplay are scarce and challenging. We aimed to establish a method to study placental nutrient transfer in humans. Focusing on glucose, we tested a hypothesis that maternal glucose concentrations and uteroplacental arterio-venous difference (reflecting maternal supply) determines the fetal venous-arterial glucose difference (reflecting fetal consumption).
  
  
  METHODS
  Cross-sectional in vivo study of 40 healthy women with uncomplicated term pregnancies undergoing planned caesarean section. Glucose and insulin were measured in plasma from maternal and fetal sides of the placenta, at the incoming (radial artery and umbilical vein) and outgoing vessels (uterine vein and umbilical artery).
  
  
  RESULTS
  There were significant mean (SD) uteroplacental arterio-venous 0.29 (0.23) mmol/L and fetal venous-arterial 0.38 (0.31) mmol/L glucose differences. The transplacental maternal-fetal glucose gradient was 1.22 (0.42) mmol/L. The maternal arterial glucose concentration was correlated to the fetal venous glucose concentration (r = 0.86, p<0.001), but not to the fetal venous-arterial glucose difference. The uteroplacental arterio-venous glucose difference was neither correlated to the level of glucose in the umbilical vein, nor fetal venous-arterial glucose difference. The maternal-fetal gradient was correlated to fetal venous-arterial glucose difference (r = 0.8, p<0.001) and the glucose concentration in the umbilical artery (r = -0.45, p = 0.004). Glucose and insulin concentrations were correlated in the mother (r = 0.52, p = 0.001), but not significantly in the fetus. We found no significant correlation between maternal and fetal insulin values.
  
  
  CONCLUSIONS
  We did not find a relation between indicators of maternal glucose supply and the fetal venous-arterial glucose difference. Our findings indicate that the maternal-fetal glucose gradient is significantly influenced by the fetal venous-arterial difference and not merely dependent on maternal glucose concentration or the arterio-venous difference on the maternal side of the placenta.
authors: Department of Obstetrics, Oslo University Hospital, Oslo, Norway.
authors: Ane M
authors: AM
authors: Holme
authors: Department of Obstetrics, Oslo University Hospital, Oslo, Norway.
authors: Marie Cecilie P
authors: MC
authors: Roland
authors: Department of Obstetrics, Oslo University Hospital, Oslo, Norway.
authors: Bjørg
authors: B
authors: Lorentzen
authors: Department of Obstetrics, Oslo University Hospital, Oslo, Norway; Norwegian National Advisory Unit on Women's Health, Oslo University Hospital, Oslo, Norway.
authors: Trond M
authors: TM
authors: Michelsen
authors: Department of Obstetrics, Oslo University Hospital, Oslo, Norway; University of Oslo, Oslo, Norway.
authors: Tore
authors: T
authors: Henriksen
mesh_terms: D000328:Adult; D001692:Biological Transport; D001786:Blood Glucose; D003430:Cross-Sectional Studies; D005260:Female; D005947:Glucose / Q000378:metabolism*; D006801:Humans; D007328:Insulin / Q000097:blood / Q000378:metabolism; D010920:Placenta / Q000378:metabolism*; D011247:Pregnancy
chemical_list: D001786:Blood Glucose; D007328:Insulin; D005947:Glucose