This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Diagnosis in obstetrics, Subject name: Gynaecology & Obstetrics
[{'content': 'On USG, blighted ovum is diagnosed when the gestational sac is : \nSelect and explain. \nA. 2 cm, B. 2.5 cm, C. 3 cm, D. 3.5 cm', 'role': 'user'}, {'content': "Answer: C \nExplanation: Blighted ovum/ Silent pregnancy: It is a sonographic diagnosis. There is absence of fetal pole in a gestational sac with diameter of 3 cm or more. Uterus is to be evacuated once the diagnosis made. Reference: Dutta's Textbook of Obstetrics 7th edition page no 161", 'role': 'assistant'}]