Pills taken orally prevents pregnancy.

Explanation

These pills contain combination of progesterone - estrogen. These pills are taken from 5th day of menstrual cycle. The process of ovulation starts after menstruation flow. The effect of these pills stops ovulation. The mucus layer of cervix becomes thick. Mucus layer of cervix becomes inactive. The entry of sperms is prevented. This way the process of fertilization is obstructed and pregnancy doesn.t take place.