2.3 Fetal echocardiographic and quantitative measurements
Fetal echocardiographic examination was performed with the heart in the anterior position. The right and left ventricular widths and lengths were measured at end-diastole in the four-chamber view. We assessed the appearance of the septum primum and the FO flap in the four-chamber view as to whether the FO had a restrictive appearance during measurement of the diameter of the FO at its maximal angle to the attachment point as defined by previous studies, with a redundant aneurysmal septum primum bulging ≥50% into the left atrium and flattening the septum, and with a FO flap swinging at less than 30° into the left atrium6,7. The inner diameters of the ascending aorta and main pulmonary artery were measured at systole in the long-axis sagittal view when the great arteries were in parallel orientation. Pulse Doppler was used to measure the flow rates of the great arteries and to assess the direction of blood flow in the DA. In terms of the constriction of the DA, we measured A peak systolic velocity in the DA of greater than 1.4 m/s was considered to be in favor of constriction8. Color Doppler was used to detect VSDs and measure its diameter both in the four-chamber view and when visualizing the outlets of the great arteries in the sagittal section of the heart. All echocardiographic measurements and quantitative findings were recorded.