Umbilical artery Doppler screening for detection of the small fetus in need of antepartum surveillance

OBJECTIVE: Our goal was to test the hypothesis that umbilical artery Doppler velocimetry identifies fetuses who are small for gestational age and in need of antenatal surveillance. STUDY DESIGN: Three hundred eight fetuses with either an ultrasonographic weight estimate <10th percentile for gestational age or an abdominal circumference <2.5th percentile for gestational age or both of these had an umbilical artery Doppler measurement of the systolic/diastolic ratio. A systolic/diastolic ratio >90th percentile for gestation was considered abnormal. The incidences of a birth weight <10th percentile, fetal distress, and metabolic acidemia were recorded for both groups (normal vs abnormal umbilical artery Doppler). RESULTS: Only the umbilical artery systolic/diastolic ratio predicted perinatal outcome in the group of fetuses who were presumed to be small for gestational age. Those 138 fetuses with elevated umbilical artery systolic/diastolic ratios had lower umbilical artery and vein pH values at birth (artery, 7.23 +/- 0.08 vs 7.25 +/- 0.1; P <.02; vein, 7.31 +/- 0.01 vs 7.34 +/- 0.09; P=.01), an increased likelihood of fetal distress consistent with chronic hypoxemia (26.3% vs 8.6%; P <.0001), more admissions to the neonatal intensive care unit (40.7% vs 30.7%; P <.005), and a higher incidence of respiratory distress (66% vs 27.3%; P <.03). However, it is important that no fetus with a normal Doppler flow measurement was delivered with a metabolic acidemia associated with chronic hypoxemia. Further, the likelihood of a false-positive diagnosis of intrauterine growth restriction was increased in the group with a normal umiblical artery Doppler resistance. CONCLUSION: Antenatal surveillance may be unnecessary in fetuses with suspected intrauterine growth restriction if the umbilical artery systolic/diastolic ratio and amniotic fluid volume are normal, because the complications that occur are intrapartum. if these findings are confirmed in prospective trials, the cost implication of reducing the number of antenatal surveillance tests administered in this group of patients is great.