Doppler flow velocimetry of the splenic artery in the human fetus: Is it a marker of chronic hypoxia?

OBJECTIVE: The aim of this investigation was to describe splenic artery flow velocity waveforms in the appropriate- and small-for-gestational-age human fetus. STUDY DESIGN: Splenic artery flow velocity waveforms were prospectively obtained from 95 appropriate- and 15 small-for-gestational-age fetuses with pulsed Doppler ultrasonography. The resistance index was used to quantify the Doppler waveform. RESULTS: A second-degree polynomial model expressed the changes of the resistance index in appropriate-for-gestational-age fetuses with advancing gestation (y = 0.057x [Weeks] - 0.001x2, R = 0.53, p< 0.001). In 14 of 15 (93%) small-for-gestational-age fetuses the splenic artery resistance index was below the mean for gestational age. In five of 15 (33%) small-for-gestational-age fetuses the resistance index of the splenic artery was <2 SEMs. A trend toward a higher hematocrit was noted in the five fetuses with splenic artery resistance index values <2 SEMs (50.2%) compared with other small-for-gestational-age fetuses 943.0%). CONCLUSION: Our results suggest that some small-for-gestational-age fetuses have decreased resistance at the level of the splenic artery. We postulate that the increased erythropoietin level, stimulated by hypoxia, results in decreased resistance at the level of the splenic artery in small-for-gestational-age fetuses. Finally, management of the small-for-gestational-age fetus may be aided by the study of the splenic artery waveforms.