The value of fetal arterial, cardiac and venous flows in predicting pH and blood gases measured in umbilical blood at cordocentesis in growth retarded fetuses

Objective To assess the value of Doppler indices, calculated from fetal arterial peripheral vessels, cardiac outflow tracts and venous vessels, in the identification of acidaemia, hypercapnia and hypoxaemia as determined by pH and gas analysis of fetal blood obtained by cordocentesis in growth retarded fetuses. Design Doppler measurements were taken from umbilical artery, thoracic descending aorta, renal artery, middle cerebral artery, cardiac outflow tracts, inferior vena cava and ductus venosus immediately before cordocentesis. Logistic regression and receiver-operator characteristic curve analysis were performed to examine the relation between Doppler indices and acid-base status. Setting Tertiary centre for fetal medicine. Subjects Forty-eight growth retarded fetuses fulfiling these criteria for inclusion: 1. absence of chromosomal and structural anomalies; 2. an abdominal circumference or ultrasonographic estimated fetal weight less than the 5th centile; 3. presence of abnormal velocity waveforms in umbilical artery; and 4. postnatal confirmation of a birthweight below the 5th centile and absence of structural anomalies. Results The percentage of reverse flow in inferior vena cava was a more closely related variable for acidaemia (chi(2) = 29.69; P < 0.001) and hypercapnia (chi(2) = 12.86; P less than or equal to 0.001) than the other Doppler indices. Hypoxaemia was better predicted by the pulsatility index from middle cerebral artery (chi(2) = 15.31; P less than or equal to 0.001). Conclusion The analysis of velocity waveforms from inferior vena cava and middle cerebral artery can be used to predict acid-base status in growth retarded fetuses secondary to placental insufficiency. This may lead to a more accurate antepartum monitoring of such fetuses.