This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: General obstetrics, Subject name: Gynaecology & Obstetrics
Blighted ovum is: 
Select and explain. 
A. Synaptic knobs, B. Avascular villi, C. Intervillous hemorrhage, D. None of the above
B: Avascular villi
Answer: B: Avascular villi 
Explanation: In missed aboion ultrasound will show a gestational sac smaller than expected with irregular and crenated margin. An embryonic pregnancy (blighted ovum )is considered when there is a gestational sac more than 16 mm in diameter without a foetal node.(refer pgno:146 sheila 2 nd edition)