Reference Ranges and Z‐Score Calculators for Pulsed‐Wave Doppler and Structural Measurements in Fetal Echocardiography Between 18 and 35 Weeks of Gestation

OBJECTIVES: To establish gestational-age-specific reference ranges and Z-score models for fetal echocardiographic measurements using a large multicenter dataset from China. METHODS: We retrospectively analyzed 22,357 fetal echocardiographic examinations conducted between 18 and 35 weeks of gestation across 3 tertiary medical centers in China. All fetuses had structurally and functionally normal hearts, confirmed by standardized echocardiographic protocols. A total of 43 cardiovascular parameters were assessed, including 13 structural and 30 pulsed-wave Doppler (PWD) measurements. Fractional polynomial regression was used to model the relationship between each parameter and gestational age (GA). Z-score models were developed using predicted means and GA-dependent standard deviations. Model performance was evaluated using residual analysis, quantile-quantile (QQ) plots, and goodness-of-fit statistics. RESULTS: Thirty-eight parameters (13 structural and 25 PWD) demonstrated satisfactory model fit. Five PWD parameters were excluded due to poor normality or inadequate regression fit. The final models showed strong statistical agreement with GA, and no mathematical transformations were necessary. Gestational-age-specific reference ranges and Z-scores were generated for each parameter, with full percentile tables provided. An online Z-score calculator (http://www.anzscore.com) was developed to facilitate clinical application. CONCLUSIONS: This study provides comprehensive reference ranges and Z-score models for fetal echocardiographic parameters based on a large Han Chinese population. These results offer a reliable foundation for prenatal cardiac assessment in Asian populations and support the development of population-specific diagnostic tools.