Antepartum improvement of abnormal umbilical artery velocimetry: Does it occur?

Abstract

Absence of end-diastolic velocity on umbilical artery velocimetry suggests extreme elevation of placental vascular resistance and is associated with adverse pregnancy outcome. This study was undertaken to assess whether antepartum improvement of abnormal umbilical artery waveforms occurs. Thirty-one fetuses identified with absence of end-diastolic velocity between July 1985 and December 1987 at Women's Hospital underwent sequential umbilical artery velocimetry at 1- to 3-day intervals. The presence of end-diastolic velocity on subsequent scans was considered an improvement in waveforms. The mean diagnosis-to-delivery interval (20.5 +/- 4 days), gestational age at delivery (32.5 +/- 1.2 weeks), and birth weight (1440 +/- 210 gm) were significantly higher in five fetuses that showed improvement in waveforms, compared with the 26 fetuses that did not show improvement in waveforms (9.5 +/- 3.5 days, 29.5 +/- 0.9 weeks, and 940 +/- 70 gm, respectively). Ten perinatal deaths occurred, for a perinatal mortality rate of 32.3%. There was significant perinatal morbidity in the overall group as judged by intrauterine growth retardation, meconium, 5-minute Apgar scores less than 7, and cesarean section for fetal distress. We conclude that although absence of end-diastolic velocity is associated with adverse pregnancy outcome, antepartum improvement in umbilical artery waveforms occurred in 15% of the fetuses studied and was associated with an improvement in perinatal outcome. Factors that influenced this improvement, though unclear, might be related to maternal bed rest or medication and require further investigation.