title: Reference ranges of blood flow in the major vessels of the normal human fetal circulation at term by phase-contrast magnetic resonance imaging.
abstract: BACKGROUND
  Phase-contrast MRI with metric-optimized gating is a promising new technique for studying the distribution of the fetal circulation. However, mean and reference ranges for blood flow measurements made in the major fetal vessels using this technique are yet to be established.
  
  
  RESULTS
  We measured flow in the major vessels of the fetal circulation in 40 late-gestation normal human fetuses using phase-contrast MRI (mean gestational age, 37 [SD=1.1] weeks). Flows were indexed to the fetal weight, which was estimated from the fetal volume calculated by MRI segmentation. The following mean flows (in mL/min per kilogram; ±2SD) were obtained: combined ventricular output, 465 (351, 579); main pulmonary artery, 261 (169, 353); ascending aorta, 191 (121, 261); superior vena cava, 137 (77, 197); ductus arteriosus, 187 (109, 265); descending aorta, 252 (160, 344); pulmonary blood flow, 77 (0, 160); umbilical vein, 134 (62, 206); and foramen ovale, 135 (37, 233). Expressed as percentages of the combined ventricular output, the mean flows±2 SD were as follows: main pulmonary artery, 56 (44, 68); ascending aorta, 41 (29, 53); superior vena cava, 29 (15, 43); ductus arteriosus, 41 (25, 57); descending aorta, 55 (35, 75); pulmonary blood flow, 16 (0, 34); umbilical vein, 29 (11, 47); and foramen ovale, 29 (7, 51). A strong inverse relationship between foramen ovale shunt and pulmonary blood flow was noted (r=-0.64; P<0.0001).
  
  
  CONCLUSIONS
  Although too small a sample size to provide normal ranges, these results are in keeping with those predicted in humans based on measurements made in fetal lambs using radioactive microspheres and provide preliminary reference ranges for the late-gestation human fetuses. The wide range we found in foramen ovale shunting suggests a degree of variability in the way blood is streamed through the fetal circulation.
authors.affiliation: From the Division of Pediatric Cardiology, Department of Pediatrics (M.P., L.S., L.G.-W., E.J., M.S.), Department of Diagnostic Imaging (J.v.A., S.-J.Y., M.S.), and Department of Physiology and Experimental Medicine (C.M.), University of Toronto and Hospital for Sick Children, Toronto, Canada.
authors.forename: Milan
authors.initials: M
authors.lastname: Prsa
authors.affiliation: From the Division of Pediatric Cardiology, Department of Pediatrics (M.P., L.S., L.G.-W., E.J., M.S.), Department of Diagnostic Imaging (J.v.A., S.-J.Y., M.S.), and Department of Physiology and Experimental Medicine (C.M.), University of Toronto and Hospital for Sick Children, Toronto, Canada.
authors.forename: Liqun
authors.initials: L
authors.lastname: Sun
authors.affiliation: From the Division of Pediatric Cardiology, Department of Pediatrics (M.P., L.S., L.G.-W., E.J., M.S.), Department of Diagnostic Imaging (J.v.A., S.-J.Y., M.S.), and Department of Physiology and Experimental Medicine (C.M.), University of Toronto and Hospital for Sick Children, Toronto, Canada.
authors.forename: Joshua
authors.initials: J
authors.lastname: van Amerom
authors.affiliation: From the Division of Pediatric Cardiology, Department of Pediatrics (M.P., L.S., L.G.-W., E.J., M.S.), Department of Diagnostic Imaging (J.v.A., S.-J.Y., M.S.), and Department of Physiology and Experimental Medicine (C.M.), University of Toronto and Hospital for Sick Children, Toronto, Canada.
authors.forename: Shi-Joon
authors.initials: SJ
authors.lastname: Yoo
authors.affiliation: From the Division of Pediatric Cardiology, Department of Pediatrics (M.P., L.S., L.G.-W., E.J., M.S.), Department of Diagnostic Imaging (J.v.A., S.-J.Y., M.S.), and Department of Physiology and Experimental Medicine (C.M.), University of Toronto and Hospital for Sick Children, Toronto, Canada.
authors.forename: Lars
authors.initials: L
authors.lastname: Grosse-Wortmann
authors.affiliation: From the Division of Pediatric Cardiology, Department of Pediatrics (M.P., L.S., L.G.-W., E.J., M.S.), Department of Diagnostic Imaging (J.v.A., S.-J.Y., M.S.), and Department of Physiology and Experimental Medicine (C.M.), University of Toronto and Hospital for Sick Children, Toronto, Canada.
authors.forename: Edgar
authors.initials: E
authors.lastname: Jaeggi
authors.affiliation: From the Division of Pediatric Cardiology, Department of Pediatrics (M.P., L.S., L.G.-W., E.J., M.S.), Department of Diagnostic Imaging (J.v.A., S.-J.Y., M.S.), and Department of Physiology and Experimental Medicine (C.M.), University of Toronto and Hospital for Sick Children, Toronto, Canada.
authors.forename: Christopher
authors.initials: C
authors.lastname: Macgowan
authors.affiliation: From the Division of Pediatric Cardiology, Department of Pediatrics (M.P., L.S., L.G.-W., E.J., M.S.), Department of Diagnostic Imaging (J.v.A., S.-J.Y., M.S.), and Department of Physiology and Experimental Medicine (C.M.), University of Toronto and Hospital for Sick Children, Toronto, Canada. mike.seed@sickkids.ca.
authors.forename: Mike
authors.initials: M
authors.lastname: Seed
mesh_terms: D000328:Adult; D001158:Arteries / Q000196:embryology / Q000502:physiology*; D003430:Cross-Sectional Studies; D005260:Female; D005315:Fetal Diseases / Q000175:diagnosis / Q000503:physiopathology; D005333:Fetus / Q000098:blood supply*; D005865:Gestational Age; D006801:Humans; D019028:Magnetic Resonance Imaging, Cine / Q000379:methods*; D011247:Pregnancy; D011296:Prenatal Diagnosis / Q000379:methods*; D011446:Prospective Studies; D012016:Reference Values; D012039:Regional Blood Flow / Q000502:physiology*; D015203:Reproducibility of Results; D014652:Vascular Diseases / Q000175:diagnosis* / Q000196:embryology / Q000503:physiopathology
keywords: magnetic resonance imaging; pediatrics; regional blood flow