How do the oral pills function a contraceptives?

CBSE Class 10 CBSE Class 10 Science
,
1

(a) How do the oral pills function a contraceptives?
(b) The use of these pills may be harmful. Why?

2

(a) They function by changing the hormonal balance of the body.
This prevents release of ova from the ovary and hence fertilization does not occur.
(b) Change in hormonal balance may cause some side effects.