Study of some physiological aspects of blood rheology in fetuses by intrauterine umbilical cord venepunctures. Relationships with hemodynamic measurements

Abstract

This study was carried on in order to describe intrauterine fetal blood rheology, and to try to correlate these measurements with hemodynamic data obtained by doppler. Fetuses underwent cordocentesis in utero during pregnancy with a method allowing an ambulatory sampling with no premedication. Pathologic cases (malformations, fetal distress) were excluded from the study. Finally, a group of 80 ‘normal’ fetuses was constituted, covering the period between 25 and 30 week's gestation. When compared to mothers studied at the same time, have significantly lower blood viscosity, lower plasma viscosity, lower RBC flexibility (measured by filterability) and higher hematocrit/viscosity ratio. Measurement of RBC rigidity by viscometry gave no significant differences. Fetal RBC aggregation was studied in 52 samples and was very low when compared to mothers with ‘M’ values equal to zero before 30 wks. The following parameters are linearly related to time: blood viscosity, hematocrit, hemoglobin count, RBC count, WBC count, eosinophil count, RBC aggregation index ‘M’. A correlation between umbilical artery resistance index and both whole blood viscosity and hematocrit is also found and requires confirmation on a larger sample.