This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Contraceptives, Subject name: Gynaecology & Obstetrics
[{'content': 'All of the following mechanisms of action of oral contraceptive pills are true, except: \nSelect and explain. \nA. Inhibition of ovulation, B. Prevention of fertilization, C. Interference with implantation of fertilized ovum, D. Interference with placental functioning', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Ans. is d, i.e. Interference with placental functioningRef: KDT 6th/ed, p314-315Even if the mechanisms by which OCP\'s act is not known to us, by sheer common sense we know that "Interference with placental functioning" is the incorrect option as if placenta is formed it means pregnancy is occurring which in itself is incorrect with regard to OCP\'s (as OCP\'s are used to prevent conception).The mechanism of action of OCP\'s in brief:* Main mechanism of action of combined pills is - prevention of ovulation.* Combined pills act by decreasing both LH and FSH* They do not interfere with placental functioning.* When taken daily for 3 out of 4 weeks, they provide virtually absolute protection against conception.', 'role': 'assistant'}]