Fetal Echocardiographic Z-Score Pilot Project: Study Design and Impact of Gestational Age and Variable Type on Reproducibility of Measurements Within and Across Investigators.

There is considerable variability in fetal echocardiographic quantification in clinical practice that may affect the design of multicenter fetal echocardiography Z-score studies, and not all measurements may be feasible for standard normalization. As missingness was substantial, a prospective design will be needed. Data from this pilot study may aid in the calculation of sample sizes and inform thresholds for distinguishing clinically significant from statistically significant effects.