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
[{'content': 'In ectopic pregnancy, the most common reaction seen in uterus is \nSelect and explain. \nA. Decidual reaction, B. Arias stella reaction, C. Double decidual sac sign, D. Stallwohy sign', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Decidual reaction : Increased structural and secretory activity of the endometrium that is brought about in response to progesterone Progesterone levels fall due to fall in the hcG levels Endometrium sloughs out causing uterine bleeding. Ref: Dutta Obs 9e pg 169.', 'role': 'assistant'}]