Background <p>Aberrant right subclavian artery is a common anatomical variant of the embryonic aortic arch, with a prevalence ranging from 0.4 to 2.0%. Although frequently associated with vascular rings or congenital cardiac defects, prenatal assessment primarily relies on the three-vessel and trachea view in ultrasonography. Currently, there is no consensus regarding whether isolated ARSA necessitates invasive diagnostic procedures. This study aimed to evaluate the necessity of routine invasive prenatal diagnosis for fetuses with sonographically isolated ARSA. By conducting a long-term postnatal follow-up of a large cohort and utilizing Bayesian analysis for risk assessment, we sought to provide empirical data to support clinical decision-making.</p> Methods <p>The fetuses diagnosed with ARSA via prenatal ultrasound at Hefei Maternal and Child Health Care Hospital from January 2019 to December 2022 were retrospectively analyzed. They were divided into isolated ARSA and non-isolated ARSA groups based on the presence or absence of other ultrasound abnormalities. Within each of these two groups, the fetuses were further categorized into diagnostic and undiagnosed subgroups based on whether they underwent invasive prenatal diagnosis. The study explored the baseline characteristics, genetic testing results, pregnancy outcomes, infant feeding and developmental status, and the results of neonatal color Doppler ultrasound re-examinations in these two groups.</p> Results <p>A total of 540 cases of ARSA fetuses were identified, including 449 cases (83.1%) of isolated ARSA and 91 cases (16.9%) of non-isolated ARSA. There were no statistically significant differences in baseline characteristics such as age, pre-pregnancy BMI, and history of diabetes between the two groups (P &gt; 0.05). However, the proportion of non-invasive prenatal testing (NIPT) applications and the pregnancy termination rate were significantly higher in the non-isolated group compared to the isolated group (P &lt; 0.05). Pregnancy outcomes revealed that there were 496 live births (91.6%), while 44 cases (8.1%) chose to terminate their pregnancies due to chromosomal abnormalities and/or severe structural abnormalities. Among the 90 fetuses that underwent invasive prenatal diagnosis, the overall detection rate of chromosomal abnormalities was 11.1%. The detection rates for isolated and non-isolated ARSA were 9.1% (6/66) and 16.7% (4/24), respectively, with no statistically significant difference between the two groups (P &gt; 0.05).The follow-up results of live births showed that 25 (5.0%) of 496 cases had abnormal phenotypes. Among 446 live births with isolated ARSA, 10 cases (2.2%) were found to have abnormal manifestations, with 1.6% (1/66 cases, diagnosed as 21-trisomy mosaicism) in the invasive diagnosis group and 2.4% (9/380 cases) in the undiagnosed group. The difference between the two groups was not statistically significant (P &gt; 0.05). In contrast, the abnormal phenotype rate of live births with non-isolated ARSA was nearly 30.0%. Bayesian risk assessment indicated that the overall posterior risk of abnormal phenotype for isolated ARSA was 2.46% (95% HDI: 1.195%-4.080%), and whether or not invasive diagnosis was performed did not alter this risk. Among the 407 live births that did not undergo invasive diagnosis, 17 cases (4.2%) exhibited abnormalities during follow-up, among whom, genetic testing identified pathogenic variants in two neonates.</p> Conclusions <p>The positive predictive value for postnatal aberrant clinical symptoms in fetuses with sonographically isolated ARSA is low (2.24%). In the absence of additional ultrasound markers or significant risk factors, routine invasive prenatal diagnosis is not recommended. Comprehensive genetic counseling should be prioritized to facilitate informed and autonomous decision-making by pregnant women and their families.</p>