Aberrant right subclavian artery (ARSA) in unselected population at first and second trimester ultrasonography

To evaluate the feasibility of examining aberrant right subclavian artery (ARSA) at first and second trimester gestation, its prevalence and associations in an unselected population.

Right subclavian artery (RSA) was prospectively evaluated in 6617 routine patients. When ARSA was detected, fetal echocardiography was offered and fetal karyotyping was discussed. If invasive testing was performed with normal karyotype, fluorescence in situ hybridization for 22q11.2 microdeletion and additionally, in case of nuchal translucency (NT) measurement above the 99(th) centile, oligo array-based comparative genomic hybridization, were offered. In all aneuploidies, NT and first trimester additional ultrasonographic (US) markers assessment (nasal bone, tricuspid valve, ductus venosus) were recorded.

RSA assessment was feasible in 85.3% and 98% of first and second trimester examinations, respectively (overall feasibility 94%). There were detected 89 ARSA (1.42% of the feasible cases), of which 66 in the first trimester. More than 20% were associated to other abnormalities: 10 aneuploidies; 2 microdeletions (15q11.2 and 22q11.2); in the euploid fetuses, 8 associated abnormalities were observed, 4 of which were cardiac defects. In the case of 22q11.2 microdeletion, ARSA was associated only with increased NT.

Prenatal routine US assessment of the RSA is feasible by highly experienced operators in first trimester screening. There is an important association of ARSA detected in unselected population with fetal abnormalities, including aneuploidies, cardiac defects and genetic anomalies. In trisomy 21 fetuses, ARSA can be the only first trimester US marker or, when associated to increased NT, it can represent the only 'additional' marker.