Internal jugular vein blood flow in normal and growth-restricted fetuses

Objective: To assess internal jugular vein blood flow patterns during the second half of pregnancy in normal and growth-restricted fetuses. Methods: We did Doppler ultrasound studies of internal jugular veins and the inferior vena cavas longitudinally on 21 normal singleton fetuses from 20 weeks to term, and on eight growth-restricted fetuses with absent end-diastolic flow at the umbilical artery (UA). The three components of the venous flow velocity waveforms were used to calculate peak velocity ratio: Peak systolic velocity (S wave) minus reverse peak velocity (R wave) divided by peak velocity during early diastole (D wave) and velocity time integral ratio: systolic velocity time integral minus reverse velocity time integral divided by velocity time integral during early diastole. Statistical analysis of longitudinal measurements used K-related samples Friedman test; groups were compared with Mann-Whitney U test and χ² test. Results: In normal fetuses we found significant increases in peak velocity ratio and velocity time integral ratio of internal jugular veins and the inferior vena cavas throughout gestation. The mean ± standard deviation (SD) of the internal jugular veins peak velocity ratio (1.12 ± 0.4 versus 1.46 ± 0.15, P < .05) and velocity time integral ratio (1.1 ± 0.2 versus 1.55 ± 0.17, P < .05) were significantly lower in growth-restricted fetuses compared with normal fetuses at 28-32 weeks' gestation but inferior vena cava indices were not. None of the eight growth-restricted fetuses had umbilical venous pulsations or changes in inferior vena cava or ductus venosus blood flow patterns. All had arterial pH above 7.15 at birth. Conclusion: Growth-restricted fetuses with absent end-diastolic velocity in the UA have changes in internal jugular vein blood flow patterns that probably indicate increased cerebral blood flow, more evidence of redistribution of blood flow in growth-restricted fetuses that can be used to maintain them. Copyright (C) 2000 The American College of Obstetricians and Gynecologists.