Ductus venosus opens in high-risk pregnancies without signs of increased central venous pressure

It has been belived that changes in diastolic blood velocities in the fetal ductus venosus were due to increased central venous pressure secondary to increased fetal heart strain during hypoxia or heart failure. There have been recent reports of changes in ductus venosus blood velocity without signs of increased fetal heart strain. The aim of this evaluation was to compare blood velocity in the right hepatic vein as a marker of increased central venous pressure in relationship to changes in ductus venosus blood velocity.

Fifty pregnancies suspected of fetal growth resitriction were evaluated by Doppler ultrasound. Blood velocity was recorded in the right hepatic vein, ducus venosus and in the umbilical vein. Placental blood flow was also recorded in the uterine and umbilical arteries as well as the fetal middle cerebral artery.

Increased umbilical artery pulsatility index was recorded in 19 fetuses and 20 has signes of brain sparing according to recordings in the middle cerebral artery. Abnormal blood velocity in the ductus venosus was recorded in 5 fetuses, none of these fetuses had an abnormal pulsatility in the right hepatic vein.

Opening of the ductus venosus is not only related to fetal cardiac strain. This might indicate that the ductus venosus does not primarily open due to increased central venous pressure in moderate fetal hypoxia. Increased fetal cardiac strain might be a late event in the process of chronic fetal hypoxia.