[Contribution of Doppler exploration of ductus venosus flow]

Among the different means currently available to assess fetal hypoxia and determine the optimal time for fetal extraction in case of intra-uterine growth retardation (IUGR), Doppler measurement of blood flow in the ductus venosus (DV) is one of the most promising. The DV is one of the three fetal circulation shunts observed in utero. Approximately 55% of the oxygenated blood flowing from the umbilical vein to the foramen ovale and the left cavities short circuits the hepatic circulation via the DV. This oxygenated blood is preferentially directed to the myocardium and the brain. Measurement errors (suprahepatic veins, umbilical veins) can lead to erroneous diagnosis of defective DV. Inversely, there is a normal physiological reverse flow in the suprahepatic veins and the inferior vena cava not present in the DV. In case of fetal hypoxia, the proportion of oxygenated blood increases due to increased flow from the umbilical vein into the DV, increasing the proportion of oxygenated blood delivered to the heart and brain instead of the liver. This corresponds to fetal adaptation to hypoxia and the spectrum of the DV thus normally includes a positive wave. When the fetus is unable to adapt to hypoxia, there is an alteration of the right heart function observable in the DV spectrum with diminished diastolic flow or even zero or reverse flow. Anomalous CV flow is a sign of major deterioration of the fetal status before development of severe anomalies. For many, the short-term variability implies immediate extraction of the fetus. Certain well trained teams combine DV flow with other information such as the biophysical examination of the fetus, the quality of the amniotic fluid, visual and automated growth retardation measurements, and other Doppler measurements for decision making. Doppler measurements of the DV, disclosing IUGR or made during surveillance of IUGR, are theoretically made only if other Doppler findings such as arterial redistribution are abnormal. Doppler assessment of DV flow is not a first intention procedure and only concerns a small high-risk fetal population. Experience and good knowledge of fetal anatomy and the Doppler technique are required (it is easy to confuse the physiological spectrum of the suprahepatic veins with a negative wave corresponding to pathological DV flow).