Growth deficient fetuses with absent or reversed umbilical artery end-diastolic flow are metabolically compromised

Controversy continues regarding the clinical relevance of absent or reversed umbilical artery blood flow during diastole. The purpose of this study was to characterize the blood gas and lactate measurements of growth deficient fetuses with absent (ADF) or reversed (RDF) umbilical artery (UA) diastolic flow. In a descriptive study from February 1988 through October 1991, 42 consecutive structurally and karyotypically normal growth deficient fetuses identified to have either ADF or RDF diastolic flow in the UA were studied. Heparinized blood specimens were obtained from them and the pH, PCO2, PO2 and lactate measured. Fourteen of these specimens were obtained from the umbilical vein by cordocentesis and 28 at the caesarean delivery of non-labouring patients. Statistical analyses were performed using Fisher's exact test, Student t-test and linear correlation. All measured parameters in fetuses with ADF or RDF undergoing cordocentesis were significantly abnormal compared to gestational age corrected norms. Both the mean venous and arterial pH of fetuses with RDF were significantly lower than that of fetuses with ADF. With few exceptions, preoperative maternal oxygenation failed to correct the fetal hypoxaemia associated with either ADF or RDF. In the setting of severe fetal growth deficiency secondary to uteroplacental dysfunction, ADF and RDF are clinically reliable indicators of fetal compromise as determined by the umbilical blood gases. RDF is associated with a greater impairment of placental gas exchange than ADF.