Measurement of epicardial fat thickness
Epicardial fat thickness was measured on the free wall of the right ventricle using a technique that showed good correlation with the values found on MRI [12, 26]. According to this method, the apical five-chamber view of the fetal heart was first obtained in a transverse plane through the fetal thorax and left ventricular outflow tract (LVOT) as the optimal view to visualize the hypoechoic space between the epicardial surface and the parietal pericardium at the right ventricle. To improve reproducibility and standardize measurements, a reference line was drawn as an anatomic landmark extending from the descending aorta through the annulus of the aortic valve and then upward to a point on the free wall of the right ventricle. The hypoechoic area at this point was used to measure EFT. Color Doppler was used to distinguish epicardial fat and pericardial effusion. A frozen real-time ultrasonographic image was acquired during end systole, and the hypoechoic area was magnified as much as possible. Then, the EFT was measured across the reference line by placing the caliper from the inside to the outside (Figure1). Measurements were taken three times and the average values were used for the final analysis.