This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Genetic and genetic disorders, Subject name: Pediatrics
Down syndrome is most commonly associated with 
Select and explain. 
A. ASD with ostium secundum, B. ASD with ostium primum, C. VSD, D. TOF
B: ASD with ostium primum
Answer: B: ASD with ostium primum 
Explanation: An ostium primum atrial septal defect (ASD) occurs when then atrial septum near the atrioventricular valves has a communication between the two atrium causing a left to right shunt. The image to the right shows the location of the different types of atrial septal defects while looking from the right atrium. 1 = Upper sinus venosus defect 2 = Lower sinus venosus defect 3 = Ostium secundum atrial septal defect 4 = Coronary sinus atrial septal defect 5 = Ostium Primum atrial septal defect Reference: GHAI Essential pediatrics, 8th edition