This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Gynaecological Disorders in Obs., Subject name: Gynaecology & Obstetrics
Most important feature to diagnose fetal aneuploidy: 
Select and explain. 
A. Absent nasal bone, B. Nuchal translucency, C. Increase in frontomaxillary angle, D. Reversal of ductus venosus flow
B: Nuchal translucency
Answer: B: Nuchal translucency 
Explanation: B i.e. Nuchal translucencyRef: Current Progress in Obstetrics and Gynecology; John Stud, Volume 1, page 17Explanation:Ultrasound Markers of Fetal Aneuploidy:Nuchal translucency is the single most powerful tool. More than 3 mm needs evaluation.Absence of nasal bone.Absence or reversal of flow in the ductus venosus on Doppler.Tricuspid regurgitation.Increase in frontomaxillary angle more than 85 deg.