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: Gynaecology & Obstetrics
Kamlesh, a 2 year old girl, has Down's syndrome. Her karyotype is 21/21 translocation. What is the risk ofrecurrence in subsequent pregnancies if the father is a balanced translocation carrier : 
Select and explain. 
A. 100%, B. 50%, C. 25%, D. 0%
A: 100%
Answer: A: 100% 
Explanation: Down Syndrome– (Trisomy 21)

Seen in 11n 800 to 1000 newborns
M/C Nonlethal trisomy
Risk of Down syndrome increases with increase in maternal age
At maternal age of 35 years, the risk of having a baby with Down syndrome is 1:365. to 1:400.

Recurrent Risk of Down’s syndrome