To explore the ultrasonographic features of fetal right aortic arch (RAA) in the first trimester.

The echocardiographic data of 12 fetuses with RAA in the first trimester who underwent standard fetal ultrasound examination and were confirmed by follow-up at Laizhou Maternal and Child Health Hospital from April 2019 to July 2022 were retrospectively analyzed, and the ultrasonic diagnostic characteristics of fetal RAA in the first trimester were summarized.

Twelve instances of RAA were observed. Among these, 8 cases were isolated RAA, and 4 cases presented with other intracardiac and extracardiac abnormalities. Three cases underwent genetic testing, 2 cases of which resulted in normal results, and 1 case of which revealed a confirmed 22q11 microdeletion. By using three vessels and trachea (3VT) view, the aortic arch of the 12 cases was located to the right of the trachea, and the distance between the ductus arteriosus and the aortic arch of the 9 cases was widened. Nine cases combined RAA with U-shaped vascular rings created by the malformed left subclavian artery and the left ductus arteriosus. Three fetal RAA cases with mirror branches on the brachiocephalic arteries (1 case without ductus arteriosus, 1 case with left ductus arteriosus, and 1 case with right ductus arteriosus) did not develop vascular rings. Two cases revealed a single artery arch (the aortic arch), while 1 case revealed the right " V" sign by using 3VT view. Eleven cases showed increased angle between aortic arch and aortic ascendens in the left ventricular outflow tract (LVOT) view of non-standard. Eight of the 12 cases were confirmed by fetal echocardiogram in the second trimester and postnatal echocardiography, and 4 cases were confirmed by autopsy.

Fetal RAA has the characteristic ultasonographic appearances in the first trimester. It is of great significance to grasp the prenatal ultrasonographic features for the early detection and diagnosis of fetal RAA.