Do abnormal Starling forces cause fetal hydrops in red blood cell alloimmunization?

Abstract

The purpose of the current investigation was to ascertain whether derangements in umbilical venous pressure and plasma colloid osmotic pressure are involved in the pathophysiologic condition of immune hydrops fetalis. Umbilical venous pressure (corrected for ambient amniotic fluid pressure) and colloid osmotic pressure were measured during intravascular transfusion. Fetal hydrops was defined as the presence of ascites by ultrasonography. The Mann-Whitney test was used for comparison of groups; a value of p < 0.05 was considered statistically significant. Fifteen hydropic fetuses were matched for gestational age with 15 nonhydropic fetuses also undergoing intrauterine transfusion for anemia. On comparison with their nonhydropic counterparts, hydropic fetuses had a statistically lower colloid osmotic pressure. Umbilical venous pressure was higher and the colloid osmotic pressure--umbilical venous pressure gradient was lower in association with fetal hydrops although these differences did not achieve statistical significance. Mild abnormalities of intravascular Starling forces may play a role in the formation of hydrops in anemic fetuses.