This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Radiotherapy, Subject name: Radiology
Most sensitive sonological indicator for aneuploidy is 
Select and explain. 
A. Gestational sac volume, B. Crown-rump length, C. Nuchal transluscency, D. Serum P HCG level
C: Nuchal transluscency
Answer: C: Nuchal transluscency 
Explanation: Ans. is 'c' i.e. Nuchal translucency Rumack writes - "The most effective sonographic marker of trisomy 21 and other chromosomal defects is increased nuchal translucency (NT) thickness at 11 to 14 weeks gestation."