Doppler ultrasonography in high-risk pregnancies - includes editor comment - adapted from the Americ

Author: Barbara Apgar
Date: Oct, 1995

Observational studies have demonstrated an association between reduced end-diastolic umbilical artery velocities as documented on Doppler ultrasonography and increased vascular resistance in fetomaternal circulation, placental pathology and adverse pregnancy results, including perinatal death. It has been suggested that the effectiveness of Doppler ultrasonography in the evaluation of flow velocity waveforms in the fetal umbilical artery should be evaluated by randomized, controlled trials before this modality is used in clinical practice. Alfirevic and Neilson conducted a meta-analysis to assess continuous-wave Doppler ultrasonography of the umbilical artery waveforms.

Twelve of the studies included in the Cochrane Pregnancy and Childbirth Group were included in the analysis. The studies were evaluated according to the "intention to treat." Primary outcome was defined as perinatal death.

Meta-analysis demonstrated that clinical action guided by Doppler ultrasonography reduced the odds of perinatal death by 38 percent. A significant reduction was apparent in the rates of antenatal admission, induction of labor and cesarean section for fetal distress in the Doppler groups, compared with control groups. Although a trend toward more preterm births occurred in the Doppler groups, the weighted difference in gestational age at delivery between Doppler and control groups was not significant. Doppler ultrasonography had no detectable effect, either beneficial or deleterious, on rates of perinatal morbidity. The only prespecified continuous outcome in this group was birth weight, and the difference between Doppler and control groups was not significant. Ten additional outcomes were available from at least one of the eligible trials. The number of elective deliveries, cases of fetal distress in labor and cases of hypoxic encephalopathy were significantly reduced in the Doppler groups.

The authors conclude that assessment of the umbilical artery waveforms by Doppler ultrasonography in high-risk pregnancies reduces the odds of perinatal death by 38 percent. The consistency of results across the trials suggests that these findings are unlikely to be due to chance. However, no strong evidence shows that Doppler ultrasonography has any impact on short-term perinatal morbidity. (American Journal of Obstetrics and Gynecology, May 1995, vol.172, p. 1379.)

EDITOR'S NOTE: This study benefits from the registry of randomized, controlled trials assembled by the Cochrane Pregnancy and Childbirth Group. The overviews, commissioned from reviewers with experience of critical appraisal of clinical research, are meta-analyses organized around groups of trials using similar interventions. The overviews focus on the effect of an intervention on a particular perinatal outcome. This registry is an invaluable source of information for clinicians practicing obstetrics.

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