RESUMO
OBJECTIVES: The aim of this study is to determine the frequency of aberrant right subclavian artery (ARSA) in trisomic and normal fetuses during the routine detailed ultrasonography in the second trimester and to evaluate the potential value of ARSA as an ultrasonographic marker for trisomy 21. METHODS: The presence of normal brachicephalic trunk/or ARSA was confirmed in all pregnant women undergoing second trimester detailed fetal anomaly screening beyond 16th week of pregnancy. Amniocentesis following genetic councelling was recommended to all women having either any positive ultrasonographic marker including ARSA or a positive biochemical screening test (triple test) result. RESULTS: During the 17-month period, 2081 patients were screened, and 23 patients with ARSA (1,1%) and 20 patients with trisomy 21 were detected. Of those 20 patients with trisomy 21, ARSA was detected in seven (%35). On the other hand, 30.4% of the fetuses with ARSA had also trisomy 21. The positive and negative likelihood ratios of ARSA for trisomy 21 were 45.08 and 0.65, respectively. CONCLUSIONS: In our study, the ARSA in combination with other ultrasound signs increased the risk for trisomy 21 by factor of 45, but the independent ability of ARSA as an isolated marker to predict fetal Trisomy 21 is unclear.