In 30 normal women with a singleton pregnancy, transvaginal Doppler ultrasound was used to record flow velocity at the fetal atrioventricular (AV) valve and outflow tract levels (ascending aorta and pulmonary artery) at 11 to 13 weeks of gestation. Technically acceptable flow velocity waveforms were recorded at the AV valve level in 19 fetuses and in the ascending aorta and pulmonary artery in 15 and 17 fetuses, respectively. Successful documentation of both transmitral and transtricuspid flow velocity waveforms was achieved in six fetuses only. Peak velocities during atrial contraction (A wave) were nearly twice as high as those during early diastolic filling (E wave), reflecting low ventricular compliance. Peak and time-averaged flow velocities in the outflow tract were lower than those observed in 2nd and 3rd trimester pregnancies with mean values of 32.1 +/- 5.4 (+/- SD) and 11.2 +/- 2.2 cm/s, respectively, in the ascending aorta and 29.6 +/- 5.1 and 10.8 +/- 2.1 cm/s in the pulmonary artery.