title: Fetal atrioventricular flow-velocity waveforms and their relation to arterial and venous flow-velocity waveforms at 8 to 20 weeks of gestation.
abstract: BACKGROUND
  Doppler ultrasonography was used to determine the nature and gestational age-related changes of human fetal AV flow-velocity waveforms and to establish their relationship with arterial impedance indexes and venous flow velocities in normal human fetuses between 8 and 20 weeks of gestation.
  
  
  RESULTS
  Flow-velocity waveform recordings were attempted in 318 singleton pregnancies. After the exclusion criteria were applied, data on 214 women were available for further analysis. Differentiation between E wave and A wave became possible at 9 weeks, whereas distinction between transmittal and transtricuspid valve flow velocities was first achieved at 10 to 11 weeks. A statistically significant nonlinear gestational age-dependent increase was established for all AV waveform parameters, which became linear when related to logarithmically estimated fetal crown-to-rump length. Transtricuspid valve flow velocities were significantly higher than transmittal valve flow velocities. Transmittal valve time-averaged flow velocities were positively correlated with peak diastolic velocities and time-velocity integral of late-diastolic reverse flow in the inferior vena cava. No correlation existed between AV time-averaged velocities and arterial impedance indexes.
  
  
  CONCLUSIONS
  Monophasic AV flow-velocity waveforms can be recorded as early as 8 weeks of gestation and become biphasic as early as 8 weeks. They demonstrate a linear increase relative to logarithmically estimated fetal crown-to-rump length, suggesting that fetal growth-related increase in volume flow plays a role in this velocity rise. Transtricuspid valve A-wave and E-wave velocities suggest right ventricular predominance as early as the late first trimester of pregnancy. AV flow velocities are not related to arterial downstream impedance.
authors.affiliation: Department of Obstetrics and Gynecology, University Hospital Rotterdam-Dijkzigt, Netherlands.
authors.forename: P
authors.initials: P
authors.lastname: van Splunder
authors.forename: T
authors.initials: T
authors.lastname: Stijnen
authors.forename: J W
authors.initials: JW
authors.lastname: Wladimiroff
mesh_terms: D000293:Adolescent; D000328:Adult; D001158:Arteries / Q000196:embryology; D016275:Atrial Function; D001783:Blood Flow Velocity; D003326:Coronary Circulation; D018568:Crown-Rump Length; D003971:Diastole; D004452:Echocardiography; D005260:Female; D005318:Fetal Heart / Q000000981:diagnostic imaging / Q000502:physiology*; D005333:Fetus / Q000502:physiology; D005865:Gestational Age; D006340:Heart Rate, Fetal; D006801:Humans; D011247:Pregnancy; D011261:Pregnancy Trimester, First; D016216:Ultrasonography, Prenatal; D014680:Veins / Q000196:embryology; D016276:Ventricular Function