2011-01-10-13 Trisomy 21 with aberrant right subclavian artery © Averyanov www.TheFetus.net
Trisomy 21 with aberrant right subclavian artery
Donetsk`s regional specialized center of medical genetic and prenatal diagnosis, Ukraine.
A 40-year-old G3 P1, a Caucasian woman with uncomplicated previous pregnancy and 1 spontaneous abortion, was referred to our center for the ultrasound examination.
On our ultrasound examination at 18 weeks we revealed the following:
Absent nasal bone
Abnormal facial features: depressed nasal bridge, upslanting palpebral fissures, prominent zygomatic arches
Clinodactyly of the little fingers
Short big toes
Aberrant right subclavian artery [1,2]
There were no gross anomalies detected. We suggested amniocentesis based on the above findings. The karyotype result confirmed trisomy 21. The parents opted for the termination of the pregnancy.
Images 1,2: Image 1 shows fetal profile, note absent nasal bone and prefrontal edema. Image 2 shows absent nasal bones.
The detection of the aberrant right subclavian artery seems to be useful tool in cases of suspected chromosomal anomaly. Presence of the aberrant right subclavian artery is much more common in fetuses with chomosomal defects than in fetuses with normal karyotype. The recent study of 2799 fetuses conducted in England showed that aberrant artery was present in 29% of fetuses with trisomy 21, 18% of cases of trisomy 18 and 8% of other chromosomal abnormal cases . The presence of the aberrant subclavian artery maybe associated with cardiac anomalies as well. 
Images 3-6: 3-5 are 3D-image of the fetal profile, note the depressed nasal bridge, prominent zygomatic arches. Mandibula seems narrow, note upslanting palpebral fissures and broad facies. Image 6 shows clinodactyly of the little finger.
Images 7,8: Images of the clinodactyly.
Image 9: Images of the short toes.
Images 10,11: Transverse view of the upper chest. Images show the aberrant right subclavian artery (ARSA) which arises as a 4th branch of the aortic arch, behind the trachea, below the level of the aortic arch, at the level of the ductus arteriosus. The left subclavian artery (LSA) arises from the aortic arch as a 3rd branch.
Note that the Doppler velocity should be changed from the setting typically used in cardiac Doppler (max velocity usually around 50-55 cm/s) to slower velocities (around 18 cm/sec) in order to detect the flow in the aberrant right subclavian artery.
Videos 1,2: The aberrant right subclavian artery.
Images 12,13: Image 12 shows a normal branching of the aortic arch. Image 13 shows the aberrant right subclavian artery which branches of the aortic arch as a 4th branch and runs behind the aorta and trachea towards the right arm.
1. Chaoui R, Thiel G, Heling KS. Prevalence of an aberrant right subclavian artery (ARSA) in fetuses with chromosomal aberrations. Ultrasound Obstet Gynecol 2006;28:414.
2. Borenstein M, Minekawa R, Zidere V, Nicolaides K, Allan L. Aberrant right subclavian artery at 16 to 23 + 6 weeks of gestation: a marker for chromosomal abnormality. Ultrasound Obstet Gynecol 2010;36:548-52.