Fetal Trisomy 21 Nuchal Nose Bone

A 39-year-old primigravida at 12 weeks and 4 days of gestation undergoes first-trimester combined screening. Transabdominal ultrasound with the fetus in a neutral mid-sagittal profile demonstrates a single live fetus with CRL 62 mm. The structure marked **B** in the diagram shows increased nuchal translucency (4.2 mm, above 95th centile for CRL) and absent nasal bone with a flat mid-face. Ductus venosus Doppler demonstrates reversed A-wave and tricuspid regurgitation (>60 cm/s). Combined first-trimester risk is adjusted to 1 in 4 for trisomy 21. Which of the following best describes the sonographic marker-set most characteristic of trisomy 21 at 12 weeks?