Explain the mode of action of contraceptive pills taken by human females. Mention the schedule to be followed for effective outcome.

• -Pills contain progestogens or progestogen – estrogen combination. -They inhibit ovulation , and implantation as well as, alter the quality of cervical mucus to prevent or retard the entry of sperms. • -Pills have to be taken daily for a period of $\displaystyle 21$ days starting within first five days of menstrual cycle. -After a gap of $\displaystyle 7$ days it has to be repeated in the same pattern till the female desires to prevent conception.