Umbilical artery flow velocity waveforms and placental resistance

the effects of embolization of the umbilical circulation

Brian J. Trudinger, Denise Stevens, Anita Connelly, J. Robert S. Hales, George Alexander, Laurence Bradley, Alan Fawcett, Rosemary S. Thompson

Research output: Contribution to journalArticle

205 Citations (Scopus)


Embolization of the umbilical placental circulation in fetal lambs was carried out to occlude the small vessels of the placental vascular bed and to observe the effect on the umbilical artery flow and flow velocity waveforms. Thirteen singleton fetuses were studied from day 120 of pregnancy. Embolization was achieved by injecting approximately 9 × 10× microspheres of 15 µm diameter into the fetal placental cotyledons along the umbilical arteries over 9 days. Umbilical and uterine flows were measured by radioactive microsphere counting. The umbilical placental resistance was increased (0.25 to 0.35 mm Hg · ml · min−1) by embolization, and there was an increase in the umbilical artery systolic/diastolic ratio. Embolization produced a significant fall in umbilical flow expressed either as total flow (312 to 237 ml · min−1) or when normalized by reference against splanchnic flow (3.36 to 1.53). We conclude that the umbilical artery flow velocity waveform systolic/diastolic ratio measures the reflection coefficient at the peripheral vascular bed (the “resistance vessels”) of the placenta.
Original languageEnglish
Pages (from-to)1443-1448
Number of pages6
JournalAmerican Journal of Obstetrics and Gynecology
Issue number6
Publication statusPublished - Dec 1987
Externally publishedYes


  • umbilical blood flow
  • flow velocity waveforms
  • embolization
  • Doppler ultrasound

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