Objective: Our purpose was to establish a reference range with gestation for umbilical venous blood pressure and to examine possible changes in intrauterine growth retardation and red blood cell isoimmunization.
Study design: Umbilical venous pressure was measured at cordocentesis in pregnancies complicated by intrauterine growth retardation (n = 20) and red blood cell isoimmunization (n = 61) both before and after intravascular fetal blood transfusion. The values were compared with a reference range that was constructed from the study of 111 pregnancies undergoing prenatal diagnosis at 18 to 40 weeks' gestation.
Results: In the control group the mean umbilical venous pressure increased significantly with gestation. In the growth-retarded fetuses umbilical venous pressure was higher, normal, or decreased, and there was no significant association between umbilical venous pressure and either fetal size or degree of acidemia. In the pregnancies complicated by red blood cell isoimmunization umbilical venous pressure increased with anemia but decreased to normal in the most severely anemic and hydropic fetuses. After intravascular blood transfusion umbilical venous pressure in proportion to the improvement in fetal hemoglobin concentration.
Conclusion: Umbilical venous pressure is not the equivalent of central venous pressure but reflects both left and right heart function and placental resistance.