This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Fetal circulation, Subject name: Pediatrics
What is the commonest aneuploidy seen in neonates born with single umbilical aery? 
Select and explain. 
A. Trisomy 18, B. Trisomy 13, C. Trisomy 21, D. Trisomy 15
A: Trisomy 18
Answer: A: Trisomy 18 
Explanation: Single umbilical aery: - It is seen in 5-10/1,000 bihs & its frequency increases in twin bihs - 30% of these infants are associated with more than one congenital abnormalities; among which Trisomy 18 is most commonest - Though it is associated with increased risk for occult renal anomaly, if no other anomalies are present, need for renal USG is controversial