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: Pharmacology
The progestogenic emergency contraceptive pills act by - 
Select and explain. 
A. Altered cervical secretion, B. Inhibition of ovulation, C. Anti-implantation effect, D. Inhibition of LH secretion
C: Anti-implantation effect
Answer: C: Anti-implantation effect 
Explanation: Ans. is 'c' i.e., Anti-implantation effect o If ovulation and feilization occur, the blastocyte fails to implant (anti-implantation effect) because endometrium is either hyperproliferativer or hypersecretory; not suitable for nidation. o This is the mechanism of action of postcoital (emergency) contraceptive pills.