Venous return to the fetal heart from the fetal brain

Abstract

Objective. To compare venous return from fetal low body and venous return from fetal brain.

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Methods. Blood flow waveforms in the inferior vena cava (IVC) and jugular vein (JV) were recorded in 30 normal fetuses at 13-16, 21-24 and 29-32 weeks of gestation (Aloka 2000). The IVC and JV flow velocity waveforms consisted of three components: the first represented forward flow during ventricular systole; the second component represented forward flow, which was coincident with early diastolic fillings; the third component depicted reverse flow reflecting atrial contraction. Time-velocity integral of forward flow (TVI FF) and time-velocity integral of reverse flow (TVI RF) were measured. Percent of reverse flow (%RF— TVI RF/ TVI FF) was calculated.

Results. In fetuses at 13-16 and 21-24 weeks of gestation reverse flow during atrial contraction expressed as %RF, was significantly greater in IVC (19,3±6,4%; 10,4±4,9%) than in JV (5,3±2,5%; 6,2±1,7%, p< 0,001). In fetuses at 29-32 weeks of gestation there was not different %RF in IVC and JV (6,2±1,7% and 5,2±2,9%, p> 0,10).

Conclusions. Our findings have suggested that fetal cardiac preload decrease with gestational age. %RF in IVC is greater than one in JV that may reflect special condition for venous return to fetal heart from fetal brain during normal pregnancy.