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 sonographic finding confirms intra uterine pregnancy 
Select and explain. 
A. An echogenic rim along one side of decidua., B. Two concentric echogenic rings surrounding the sac., C. A sac positioned eccentrically within endometrium., D. All of the above.
D: All of the above.
Answer: D: All of the above. 
Explanation: Normal gestational sac implants eccentrically in the endometrium.
Anechoic center surrounded by single echogenic rim = intra-decidual sign.
Two concentric rings echogenic surrounding sac = Double decidual sign.