The aortic and pulmonary outflow tract screening examination in the human fetus.

Imaging of the aortic and pulmonic outflow tracts in the fetus may be difficult owing to fetal position. This study describes two screening methods for imaging the outflow tracts, depending on whether the interventricular septum was tangential (group I) or perpendicular (group II) to the ultrasonic beam. We performed 170 examinations during the second and third trimesters of pregnancy. The outflow tracts were imaged in 166 (97.6%). Fetuses in group I were identified much less frequently (13.2%) than fetuses in group II (86.8%). This study would suggest that for the outflow tracts to be imaged during a screening examination, the sonographer should become familiar with the sonographic anatomy of the outflow tracts when the interventricular septum is perpendicular to the ultrasound beam.