Intracardiac blood flow velocity waveforms in normal fetuses in utero.

Sixty-five continuous-wave Doppler ultrasonographic examinations were performed on 57 normal fetuses at 16 to 40 weeks of gestation. Maximal velocities of transmitral, transtricuspid, transaortic and transpulmonary blood flow velocity waveforms were assessed. Transmitral maximal velocity, transtricuspid maximal velocity, transaortic maximal velocity and transpulmonary maximal velocity correlated well with gestational age. The ratio of transtricuspid maximal velocity/transmitral maximal velocity was at least 1 in 44 of 45 fetuses (97.8%). In the ratio of transpulmonary maximal velocity/transaortic maximal velocity, the characteristic change was not evident. Therefore, continuous-wave Doppler ultrasonographic measurement of fetal intracardiac blood flow velocity waveforms in utero can aid in analyzing the physiologic circulatory hemodynamics.