The sonographic 3-vessel view (3VV) of the fetal heart provides a transverse orthogonal image of the fetal upper mediastinum that allows assessment of great artery asymmetry during fetal development. A number of studies have demonstrated that the fetal ascending aorta (AA) is normally equal to or slightly smaller than the fetal main pulmonary artery (MPA) throughout gestation and that a ratio of AA/MPA greater than 1 may suggest congenital heart disease (CHD). This case study assessed the association of CHD with an AA/MPA ratio above 1 among a series of 2797 fetal echocardiographic examinations performed by the investigators using 3VV sonography.
Examination of the 2797 fetal echocardiograms with the 3VV identified 31 fetuses (1.1%) with AA/MPA ratios greater than 1. All 31 had evidence of CHD. Twenty-five (81%) had either tetralogy of Fallot (ToF) or a variant, and 6 (19%) had an aortic valve abnormality or isolated dilatation of the AA. These findings in the largest series reported to date demonstrate that a 3VV AA/MPA ratio of greater than 1 is strongly associated with CHD and indicates the need for a detailed fetal echocardiogram.