Z -score of some pulsed-wave Doppler indices of right pulmonary artery segments of normal fetuses in the second and third trimestries.

Objective: To establish the Z -score equation of right pulmonary artery (RPA) segments for some valuable pulse-wave Doppler parameters (PWD) and estimate their reference ranges in normal fetuses.
Methods: Two hundred and seventy-three normal singleton fetuses at 18-38 weeks were enrolled in this fetal echocardiography of a prospective cross-sectional study. The proximal, middle, and distal segments of RPA of pulsed-wave Doppler parameters, such as peak systolic velocity (PSV) and pulsation index (PI) were obtained by using fetal Doppler echocardiography. The mean and standard deviation (SD) of each parameter and gestational age (GA) were analyzed by regression, and the optimal model of Z -score was established.
Results: There was a significant correlation between fetal pulmonary artery Doppler parameters and gestational age, during the whole pregnancy, PI showed a downward trend with the progress of gestational week, while PSV showed an upward trend. Whether it was the original data or the data converted for the normal distribution of Z -score, the model that best described the mean value of parameters was quadratic regression. The SDs for PSV of the middle segment was a linear equation, others were constants. From proximal to distal of RPA, PSV showed a decreasing trend while PI showed an increasing trend.
Conclusion: Z -score models and reference values for some PWD parameters of three segments of RPA were proposed against GA, which may quantitatively assess the flow dynamics of fetal RPA and quantitatively assess fetal lung circulation development and hemodynamic changes.