[Study on intracardiac blood flow with color flow mapping in human fetus--the reverse flow at tricuspid valve in human fetus during labor].

This study was performed to determine the relation among the reverse flow signal of tricuspid valve, fetal heart rate pattern and uterine contraction. The blood flow signal through the tricuspid valve was continuously recorded with color flow mapping and direct fetal electrocardiogram as well as uterine contraction in 17 human fetuses during labor. Gestational ages ranged from 36 to 41 weeks. No fetus had a congenital heart anomaly. The detection rate of the reverse flow signal at the tricuspid valve was 100% in variable deceleration, 33% in late deceleration, 5% in normocardia and none in early deceleration. In investigation of the time relation between the reverse flow signal and variable deceleration, the reverse flow signal started after the onset of the recovery phase of deceleration. The tricuspid reverse flow, which was observed in variable deceleration, was caused by an increase in the venous return when cord compression disappeared at the onset of the recovery phase of variable deceleration.