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
[{'content': 'Most important feature to diagnose fetal aneuploidy: \nSelect and explain. \nA. Absent nasal bone, B. Nuchal translucency, C. Increase in frontomaxillary angle, D. Reversal of ductus venosus flow', 'role': 'user'}, {'content': 'Answer: B \nExplanation: 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.', 'role': 'assistant'}]