<prompt> Mechanism of action of Combined OCP pills:Prevent fertilizationPrevent release of ovum from ovaryPrevent implantation of fertilized ovumReduce sperm motility  <response>: Ans. b Prevent release of ovum from ovaryRef: K. Park 23rded. 501 Combined oral contraceptive pills act by inhibiting ovulation by suppressing the release of gonadotropins. Continuous progesterone by OCPs which give negative feedback to GnRH, which decreases LH release and upto some extent FSH release also. This prevents LH surge and as a result inhibits ovulation. 