Fig. 1

a. The position of regions of interest (ROI) with size 6 × 4 mm in an anemic fetus before intrauterine transfusion at 34 weeks of gestation. The left panel indicates the position of ROIs in the four-chamber view of the fetal heart at end-diastole. The right panel shows the myocardial velocity trace derived from the right ventricular wall. b. The same myocardial velocity trace analyzed by the automated algorithm. Colors indicate different phases in the cardiac cycle: dark blue – atrial contraction, light green – pre-ejection, red – ventricular ejection, dark green – post-ejection, yellow – rapid ventricular filling and light blue – slow ventricular filling. Sm, peak myocardial velocity during ventricular ejection (systole); Em, peak myocardial velocity during rapid ventricular filling; Am, peak myocardial velocity during atrial contraction