title: The influence of spontaneous accelerations of fetal heart rate on umbilical artery velocity waveforms.
abstract: For clinical interpretation of Doppler waveforms, it is important to establish the extent to which fetal heart rate changes affect the umbilical artery velocity waveform. Umbilical artery waveforms were measured with continuous wave ultrasonography during spontaneous accelerations of the fetal heart rate in 20 uncomplicated, near-term pregnancies. On average, an acceleration of 20 beats/min of fetal heart rate within an individual was associated with a reduction in the systolic/diastolic velocity ratio of 0.25. There was, however, considerable variability in the response, and in six patients the systolic/diastolic ratio actually increased with heart rate. We conclude that fetal heart accelerations within the normal range cause only small and variable changes in the systolic/diastolic ratio.
authors.affiliation: Department of Obstetrics and Gynaecology, Mount Sinai Hospital, Toronto, Ontario, Canada.
authors.forename: R J
authors.initials: RJ
authors.lastname: Morrow
authors.forename: S L
authors.initials: SL
authors.lastname: Adamson
authors.forename: M
authors.initials: M
authors.lastname: Lewin
authors.forename: S B
authors.initials: SB
authors.lastname: Bull
authors.forename: J W
authors.initials: JW
authors.lastname: Ritchie
mesh_terms: D001783:Blood Flow Velocity; D001794:Blood Pressure; D005260:Female; D006340:Heart Rate, Fetal; D006801:Humans; D011247:Pregnancy; D011263:Pregnancy Trimester, Third; D014469:Umbilical Arteries / Q000502:physiology*