Fetal pulmonary venous blood flow velocities in a normal population and new calculated reference values.

Objective The aim of this study is to establish new Doppler reference values in a population with normal pulmonary veins during different phases of the fetal cardiac cycle for maximum blood flow velocities during ventricular systole (S), early ventricular diastole (D), atrial contraction (a), intensity-weighted mean velocity (Vmean) and the indices derived from these parameters [(S - a)/D] and [(S - a)/Vmean]. Methods The pulsed-wave color advanced dynamic flow Doppler technique was used in a prospective cross-sectional study of 365 low-risk pregnancies between 18 and 41 completed gestational weeks. Reference ranges were calculated for the individual measuring parameters based on a growth function from a four-parameter class of monotonic continuous functions according to the smallest square principle. Results During the observation period of 18 to 41 gestational weeks, a continuous increase was evident in maximum flow velocities for ventricular systole (S), early ventricular diastole (D), atrial contraction (a) and intensity-weighted mean velocity (Vmean) of 14.7 to 431.1, 12.5 to 426.2, 5.4 to 411.9 and 8.7 to 421.6 cm/s, respectively. Venous indices, however, showed a decrease with increasing gestational age: (S - a)/D from 0.9 to 0.7 and (S - a)/Vmean from 1 to 0.9. Conclusion The newly established normal values for the fetal pulmonary vein can be used in standardized Doppler sonography measurement to assess the left atrial pressure in the fetal heart. (C) 2016 John Wiley & Sons, Ltd.