Are emergency contraceptives really helps to avoid pregnancy?

Yes: What they do is prevent implantation of a possible fertilized ovum. If you believe that life begins at conception, then you would essentially be destroying a life.

Yes if used in: a timely manner. Plan B One-Step is up to 89 % effective when taken within 72 hours (3 days) after unprotected sex. It can reduce chance of pregnancy by up to 95% if used within 24 hours. It continues to reduce the risk of pregnancy up to 120 hours (5 days) after unprotected sex, but is less effective as time passes.