Continuous wave Doppler flow velocity waveforms from the umbilical artery in normal pregnancy

J Perinat Med. 1990;18(1):51-7. doi: 10.1515/jpme.1990.18.1.51.


The objective was to establish a normal reference range of the indices of umbilical artery waveforms using continuous wave doppler ultrasound. A prospective longitudinal study was made of 85 uncomplicated singleton pregnancies between 16 and 40 weeks gestation (783 recordings). Pulsatility Index (P.I.), Resistance Index (R.I.) and A/B ratio were measured at each visit. The mothers all delivered normal healthy infants weighing more than the 10th centile for gestational age. All three indices have a positively skewed frequency distribution, a factor not generally appreciated until recently and the ranges are therefore described using non-parametric statistics. Placental resistance decreases as term approaches, the 50% PI at 16 weeks was 2.06, at 32 weeks was 1.08 and at 40 weeks was 0.85. The results show a comprehensive reference of normal values and provides a sound basis for the further study of abnormal pregnancy. It represents the largest published study of its type using continuous wave Doppler.

MeSH terms

  • Adolescent
  • Adult
  • Blood Flow Velocity
  • Female
  • Fetal Blood*
  • Gestational Age
  • Humans
  • Longitudinal Studies
  • Pregnancy
  • Prospective Studies
  • Reference Values
  • Ultrasonics
  • Umbilical Arteries / physiology*