This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Advanced Fetal Ultrasonography and Therapy, Subject name: Radiology
USG can detect gestational sac earliest at- 
Select and explain. 
A. 5 - 6 weeks, B. 7 - 8 weeks, C. 8 - 10 weeks, D. 10 - 12 weeks
A: 5 - 6 weeks
Answer: A: 5 - 6 weeks 
Explanation: Ans. is 'a' i.e., 5-6 weeks [Ref: Sutton 7th/ep. 1041)o The gestational sac can be visualized as early as 41/2 weeks by transvaginal USG and 5 weeks by transabdominalUSG