Fetal Proximal and Distal Transverse Aortic Arch and Aortic Isthmus Measurements Between 19 and 34 Weeks of Gestation

To assess fetal proximal and distal transverse aortic arch and aortic isthmus (AI) diameters between 19 and 34 weeks of gestation. A prospective cross-sectional descriptive study was performed in 466 low-risk pregnancies between 19 and 34 weeks of gestation. Proximal transverse aortic arch (PTAA), distal transverse aortic arch (DTAA), and the AI diameters (sagittal and three-vessel trachea view) were measured. The mean ± SD, and 5th, 50th, 95th centile charts according to gestational age for PTAA, DTAA, and AI diameter were constructed. Pearson's correlation coefficients for PTAA, DTAA, and AI diameter (sagittal and three-vessel trachea view) by gestational week were 0.884, 0.877, 0.890, and 0.898, respectively (P < .0001). The mean AI diameter, in both sagittal and three-vessel trachea planes, was significantly lower than that of the proximal and distal transverse aortic arch (P = .001). We demonstrated the growth curve and nomogram of the PTAA. With the aid of nomograms, the prenatal identification of proximal transverse aortic arch hypoplasia may facilitate a better understanding of the severity of transverse aortic arch hypoplasia and assist in planning the appropriate postnatal surgical intervention.