Ranged-Gated Pulsed Doppler of the Umbilical Artery in Human Fetuses During Normal Pregnancies

ABSTRACT

Range-gated pulsed Doppler has permitted the study of umbilical artery flow velocity waveforms (FVWs) in human fetuses and is becoming part of the antepartum fetal evaluation. No uniform method of describing such velocity waveforms and no significant body of normal values using pulsed Doppler can be found in the literature. The present study reports on a cohort of 268 patients who had pulsed Doppler umbilical artery FVWs performed during their pregnancy. The gestational age at the time of the study ranged between 16th and 42nd weeks of gestation in normal pregnancies. The systolic to diastolic (S/D) ratio was found progressively to decrease as gestation advanced; however, the range of normal values in this study was found to be quite large at all gestational ages. The present data represent normative data of the umbilical artery FVWs S/D ratio in a large number of normal pregnancies as shown by the follow-up of all the patients to delivery. Before umbilical artery waveform becomes part of the antenatal armamentarium, we advise caution before adopting rigid values that are derived from small groups. Lack of standard values for the 95th percentile may result in a premature delivery of an otherwise normal fetus.