To evaluate the clinical value of echocardiography in detecting fetal coarctation of the aorta, and to explore the optimal echocardiographic parameters to improve the diagnosis accuracy.

Fetuses with suspected CoA diagnosed at Fuwai Hospital between December 2017 and July 2019 were enrolled and divided into two groups based on the aorta arch growth after birth. There were 18 fetuses with CoA and 14 with normal aorta arch. The t-test was used to analyze the differences between the two groups. Receiver operating characteristics curve analysis was performed to determine the optimal cut-off values of diagnostic parameters, and the kappa test was used to determine the diagnostic accuracy of the proposed model.

Compared with the fetuses with normal aorta arch, the fetuses with CoA had lower Z values of the isthmus[(-6.54±1.61) vs (-8.4±1.61), t=2.491, P=0.003], smaller angles between the transverse arch and the isthmus [(126.2±13.4)° vs (95.4±20.9)°, t=4.787, P＜0.001], and increased distances between the left subclavian artery and the left common carotid artery [(4.6±2.5) mm vs (2.9±1.3) mm, t=-2.186, P=0.037]. The angle between the transverse arch and isthmus ≤ 110.47°, the diameters of the transverse arch ≤ 2.25 mm, and the Z values of the isthmus ≤ -7.98 were the optimal cutoff values to detect fetal CoA. The combination of the angle between the transverse arch and the isthmus and the diameters of the transverse arch and isthmus to identify fetal aortic arch growth had the highest consistency with postnatal results (Kappa=0.936, P＜0.001).

The angle between transverse arch and the isthmus is the optimal parameter to identify fetal CoA. The combination with other multiple echocardiographic indices could improve the prenatal diagnosis of fetal CoA.