How effective is emergency contraception (plan b) after the first 72 hours?

Plan B. 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.
About same. According to a study published in 2010, there were 2.6% pregnancy when taken within first 3 days and 1.5% when taken between 3-5 days. This does not mean it works better when taken later but certainly suggests taking 3-5 days after is still worthwhile. Paper here: http://www.Thelancet.Com/journals/lancet/article/piis0140-6736(10)60101-8/abstract.