[Right subclavian artery evaluation during first trimester ultrasound scan]

To determine the feasibility of evaluation of the right subclavian artery during the first trimester ultrasound scan, as well as to describe the technique for its evaluation and, in case of aberrant right subclavian artery (ARSA) identification, to determine its association with chromosomal abnormalities and/or cardiac malformations and its management.

A prospective study for evaluation of the right subclavian artery during the first trimester ultrasound scan (crown-to-rump length between 45 and 84 mm), in all consecutive single pregnancies, by a single examiner, using a Voluson E8 system (GE Healthcare, Zipf, Austria) with a 2 to 8 MHz RAB 4-8-D transabdominal probe, within a short period of time (less than 2 minutes), in a general low risk population. Color and/or power Doppler flow mapping was used to classify the right subclavian artery as normal or aberrant. Regression analysis with the IBM SPSS Statistics software for Windows, version 20.0 was used to determine the significance of the association between failure to examine/classify the right subclavian artery and both fetal crown-rump length and maternal body mass index.

Median maternal age was 30 years (range: 17-43 years) and median gestational age at the time of evaluation of the right subclavian artery was 12 weeks (range: 11-13 weeks). The evaluation of the right subclavian artery was successful in 138/176 (78.4%) of the cases. ARSA was diagnosed in a single case (0.7%). This fetus with ARSA also presented a hyperechogenic focus on the left cardiac ventricle. Fetal echocardiography at 16 weeks of gestation was performed and confirmed ARSA and the hyperechogenic focus. Amniocentesis revealed a normal 46, XX karyotype.

ARSA can be identified during a routine first trimester ultrasound scan. Our single ARSA case had a normal karyotype and no associated cardiac malformations.