Prenatal Diagnosis of Aberrant Right Subclavian Artery in Unselected North Indian Population: Significance and Counselling

Abstract

AbstractThis study was carried out to assess the incidence and association of aberrant right subclavian artery in North Indian population and to analyse its significance as a marker of Down syndrome and to formulate an adaptable protocol for counselling and management of such pregnancies. A prospective assessment of 1024 consecutive unselected pregnancies with gestational age between 12 and 34 weeks was carried out from May 2016 to August 2017 at the author’s fetal medicine centre in North India. The screening for ARSA was performed with Color Doppler using low PRF at 3 vessel trachea view in axial section followed by confirming of arterial flow pattern by pulse Doppler. Incidence of ARSA in this study was 0.58%. Thirty-three percent of cases of ARSA were associated with other anomalies whereas 66% were isolated. Trisomy 21 was found in 16.6% of cases. ARSA as a marker of Trisomy 21 has a high specificity (99%) but low sensitivity (33%, [95% CI]). Although global likelihood ratio (LR) for ARSA as a marker for Down syndrome was high, the LR for isolated ARSA was nil. Isolated ARSA can be considered a normal variant and does not warrant invasive prenatal diagnosis in the scenario of low biochemical risk. On the other hand, ARSA associated with other markers/anomalies warrants invasive prenatal diagnosis.