To assess the possibilities of first trimester prenatal diagnosis of aberrant right subclavian artery (ARSA). A prospective study of 283 singleton pregnancies scanned between 11-13+6 weeks of gestation (w.g.) was performed in MC “Markovs”, Sofia between Jun 2015 and Feb 2016. All cases were examined in B-mode and ultrasound screening for fetal abnormalities was performed according to standard published guidelines. In addition, the natural course of the right subclavian artery (RSA) was also identified by Colour Doppler. All continuing pregnancies were followed-up by ultrasound in the second trimester. No false-positive or false-negative cases of ARSA were found. Overall 5 cases of ARSA were detected in the first trimester throughout the study period. In 4 of them ARSA was an isolated finding. In the last case the nuchal translucency was also increased. Fetal karyotyping revealed an associated Trisomy 21 and the parents opted for termination of pregnancy. Visualisation of RSA is relatively easy during the 11-13+6 w.g. scan. Since the association between ARSA and chromosomal fetal abnormalities is well established, the implementation of its sonographic evaluation might improve the sensitivity of the first trimester screening.