title: Left-right difference in fetal liver oxygenation during hypoxia estimated by BOLD MRI in a fetal sheep model.
abstract: OBJECTIVE
  The purpose of this study was to measure differences in oxygenation between the left and right sides of the fetal liver during varying oxygenation levels.
  
  
  METHODS
  Eight ewes carrying singleton fetuses at gestational age 125 days (term, 145 days) were included in the study. Under anesthesia the ewes were ventilated with gas containing different levels of oxygen, thereby subjecting the fetuses to hyperoxia (mean ± SD maternal arterial partial pressure of oxygen (pO2), 23.2 ± 8.2 kPa) and hypoxia (mean maternal arterial pO2, 7.1 ± 0.5 kPa). Changes in oxygenation within the fetal liver were assessed by blood oxygen level-dependent (BOLD) magnetic resonance imaging (MRI).
  
  
  RESULTS
  During hyperoxia there was no difference between the BOLD signal in the left and right sides of the fetal liver; mean change in BOLD (ΔBOLD)(hyperox), -0.9 ± 3.7%. During hypoxia, however, the decrease in the BOLD signal was more pronounced in the right side as compared with the left side, thereby creating a significant increase in the left-right difference in the BOLD signal; mean ΔBOLD(hypox), 5.2 ± 2.2% (P = 0.002, paired t-test). The left-right difference was directly proportional to the degree of hypoxia (R2 = 0.86, P = 0.007).
  
  
  CONCLUSIONS
  To our knowledge, this is the first study demonstrating differences in oxygenation between the left and right sides of the fetal liver during hypoxia, a difference that can be explained by increased ductus venosus shunting. Thus, the BOLD MRI technique is a promising non-invasive tool that might be useful for the future monitoring of the human fetus.
authors.affiliation: Department of Gynecology and Obstetrics, Aarhus University Hospital, Aalborg, Denmark. ans@rn.dk
authors.forename: A
authors.initials: A
authors.lastname: Sørensen
authors.forename: D
authors.initials: D
authors.lastname: Holm
authors.forename: M
authors.initials: M
authors.lastname: Pedersen
authors.forename: A
authors.initials: A
authors.lastname: Tietze
authors.forename: B
authors.initials: B
authors.lastname: Stausbøl-Grøn
authors.forename: L
authors.initials: L
authors.lastname: Duus
authors.forename: N
authors.initials: N
authors.lastname: Uldbjerg
mesh_terms: D000818:Animals; D005260:Female; D005311:Fetal Hypoxia / Q000175:diagnosis / Q000378:metabolism / Q000503:physiopathology*; D008099:Liver / Q000196:embryology / Q000378:metabolism / Q000503:physiopathology*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D010100:Oxygen / Q000097:blood; D010101:Oxygen Consumption; D011247:Pregnancy; D034561:Sheep, Domestic
chemical_list: D010100:Oxygen