<prompt> USG can detect gestational sac earliest at-5 - 6 weeks7 - 8 weeks8 - 10 weeks10 - 12 weeks  <response>: Ans. is a i.e., 5-6 weeks Ref: Sutton 7thep. 1041o The gestational sac can be visualized as early as 412 weeks by transvaginal USG and 5 weeks by transabdominalUSG 