This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Pediatrics
Increased nuchal fold thickness is a feature of – 
Select and explain. 
A. Paul–Bunnel syndrome, B. De–pan syndrome, C. Down's syndrome, D. Cri–duchat syndrome
C: Down's syndrome
Answer: C: Down's syndrome 
Explanation: Nuchal fold thickness is increased in Down syndrome. This feature is used in suspecting the diagnosis of Down's syndrome prenataly.
Down's syndrome 

Down's syndrome is due to trisomy 21.
Down's syndrome is the most common trisomy.
In this condition, extra genetic material causes a delay in the way a child develops and often leads to mental retardation.
In Down's syndrome the child gets on the extra chromosome, he has a total of 47 chromosomes instead of 46 chromosomes.
This is the extra genetic material that causes the physical and cognitive delays associated with Down's syndrome.
There is a well-recognized association with advanced maternal age, the risk considerably increases in women > 35 years of age.
Advanced paternal age has no effect.