Systemic assessment of fetal hemodynamics by Doppler ultrasound

The aim of our study was to investigate the parameters of fetal circulation of normal pregnancies and their relationship to fetal cardiac output. We p erformed a cross-sectional study of 315 normal singleton pregnancies betwee n 20 and 40 weeks' gestation without fetal chromosomal or structural malfor mations, After follow-up to delivery, 212 patients who fit all the criteria were enrolled for final analysis. Blood flow velocity waveforms were obtai ned from the tricuspid and mitral ventricular inflow, ascending aorta (AAO) , pulmonary artery (PA), middle cerebral artery (MCA), renal artery (RA), u mbilical artery (UA), descending aorta (DAO), inferior vena cava (IVC) and ductus venosus (DV) using duplex (real-time Doppler) ultrasound (US) scanne r. The peak velocity of DV, AAO, PA and MCA were also obtained. At the intr acardiac level, the ratio of peak flow velocity of E wave to peak flow velo city of A wave (E:A ratio) of mitral valve (MV) increased more rapidly than tricuspid valve (TV) E:A ratio. For the great vessels, aortic peak velocit y remained higher than the pulmonary peak velocity with advancing gestation . The cardiac output closely correlated to the cardiac compliance and dow r esistance indices at arterial and venous level. The acceleration time in th e fetal arteries increased with advancing gestation in AAO, PA, MCA and DAO , but it decreased in EA and kept constant in UA, In addition, the accelera tion time of UA was unrelated to cardiac output. The changes of the fetal i ntracardiac, arterial and venous impedances were remarkable through the ges tation and related to cardiac output. Fetal cardiac output correlated well with the changes of arterial resistance, except with the DAO, The ventricul ar compliance increased with advancing gestation, especially in the left si de, and was highly related to the change of cardiac output. The acceleratio n time in major arteries positively correlated with the gestational age and cardiac output, except in UA and RA; this indicates the difference of the changes of mean arterial pressure in uteroplacental circulation, fetal orga ns and great vessels. In conclusion, the fetal cardiac output correlated we ll with the ventricular compliance and was influenced by both hemodynamic c hanges in peripheral resistance and mean arterial pressure. (C) 2000 World Federation for Ultrasound in Medicine & Biology.