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
Which of the following is not a sonographic criterion for cesarean scar pregnancy 
Select and explain. 
A. Anterior uterine isthmic mass, B. Hourglass uterine shape, C. Empty cervical canal, D. Hyperechoic thin endometrial stripe
B: Hourglass uterine shape
Answer: B: Hourglass uterine shape 
Explanation: Sonographic criteria for cesarean scar pregnancy include 

Empty uterine cavity - bright hyperechoic endometrial stripe
Empty cervical canal
Intrauterine mass seen in anterior part of uterine isthmus.