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
Embryonic structure, identified earliest on USG, for confirmation of pregnancy is: March 2011, March 2013 
Select and explain. 
A. Fetal pole, B. Fetal Hea activity, C. Gestation sac, D. Fetal skeleton
C: Gestation sac
Answer: C: Gestation sac 
Explanation: Ans. C: Gestation sac Gestation sac and embryonic yolk sac is identified at menstrual age of 5 weeks Fetal pole and cardiac activity is identified on USG at menstrual age of 6 weeks Lower limb buds, upper limb buds and spine at 7, 8 and 9 weeks respectively Remember: Total duration of pregnancy: 280 days Earliest detection of pregnancy by USG: Gestational sac Pregnancy is confirmed by: - Fetal hea rate - Fetal sac on USG - Fetal movements Transvaginal sonography detects gestational sac: at 14 days after ovulation