Fig. 2

Normal ultrasonography of fetal thorax. a normal ultrasonography of fetal heart four-chamber view section; b normal ultrasonography of fetal three vessels trachea view section. H: heart, ThAO: thoracic aorta, SP: spine, LL: left lung, RL: right lung, SVC: superior vena cava, mPA: main pulmonary artery, ARCH: aortic arch, T: trachea, TH: thymus