Objective. To evaluate the changes of uteroplacental, fetal aorta and umbilical circulation during early pregnancy (from 7 to 16 weeks' gestation) in non-complicated pregnancies. Material and methods. A 5-MHz broad-band transvaginal sonographic transducer combined with pulsed color Doppler was used to scan 42 healthy volunteer pregnant women. Results. Vascular impedance to blood flow in all examined vessels decreased significantly throughout the first gestational trimester Resistance to flow was highest in the main uterine artery and decreased towards the spiral artery. When the flow velocity waveform patterns of the arteries under investigation were analyzed, specific changes were observed. In all cases during early gestational development, an early diastolic notching was determined in the uterine arteries. The flow velocity waveforms of the fetal aorta and umbilical artery were similar: until week 10 the arteries were typically without diastolic flow. From week 16 onwards, diastolic velocities were present in all signals at the fetal aorta and umbilical artery Conclusion. Fetal and uteroplacental velocities increase gradually during early pregnancy, and velocimetric indices show a progressive decrease of the fetal and uteroplacental resistances. However, Doppler sonography in the first trimester of pregnancy is not a routine diagnostic tool, although it has potential to reflect the pathophysiological changes in early pregnancy
