ACCURACY OF THE UMBILICAL ARTERIES DOPPLER FLOW VELOCITY WAVE-FORMS IN DETECTING ADVERSE PERINATAL OUTCOMES IN A HIGH-RISK POPULATION

Objective. To define the accuracy of the umbilical artery Doppler flow velocity waveforms, according to different cut-off values, in predict ing adverse perinatal outcomes among fetuses at high risk of hypoxic c omplications. Subjects. Two hundred and sixty-five pregnant women with diagnosis of small for gestational age fetus and/or pregnancy induced hypertension studied in four Italian ultrasound units. Methods. Prosp ective study. Serial Doppler ultrasound measurements of the umbilical artery were performed. Results were not available for clinical managem ent. Cut-off curves, corresponding to different age-specific centiles of the pulsatility index distribution among pregnancies resulting in h ealthy newborns, regardless of birthweight, were computed by regressio n methods. Sensitivity, specificity, positive predictive value and neg ative predictive value of such cut-off curves, and of absent/reverse e nd-diastolic flow, in predicting different adverse outcomes were estim ated. The adverse outcomes were: perinatal or neonatal death (OUTCOME I). Death or Apgar<7 at 5' or need for admission to intensive care uni t or other hypoxic related abnormalities (OUTCOME 2). Either OUTCOME 2 or birthweight<10th centile (OUTCOME 3). Both OUTCOME 2 and birthweig ht<10th centile (OUTCOME 4). Results. The best accuracy was in predict ing OUTCOMES 1 and 4. Positive predictive value increased strongly wit h higher cut-off curves while negative predictive value only decreased slightly. For absent/reverse end-diastolic how negative predictive va lue and positive predictive value were respectively 94% and 39% for de ath, and 81% and 72% respectively for OUTCOME 2. For the 95th centile curve the corresponding figures were 96%, 33% and 84%, 67%. The 60th c entile curve had a 85% and 74% sensitivity value for death and OUTCOME 2 respectively, but the corresponding positive predictive values were 18% and 40% only. Conclusions. The findings of an absent end diastoli c how or of pulsatility index values above the 95th centile curve stro ngly suggest it is time to deliver the fetus. The 60th centile curve i s the most suitable to recognize fetuses at risk for abnormal outcome, but early delivery should be avoided because of its low positive pred ictive value.