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
Earliest ultrasound sign of pregnancy in a transabdominal ultrasound scan is : 
Select and explain. 
A. Visible gestational sac, B. Apparent embryonic structures, C. Fundal endometrial thickening, D. Identifiable cardiac movements
C: Fundal endometrial thickening
Answer: C: Fundal endometrial thickening 
Explanation: Fundal endometrial thickening