According to WebMD, if the morning-after pill is taken within 24 hours after having sexual intercourse, then it is deemed to be 95 percent effective at preventing pregnancy. However, if the emergency contraceptive is taken between 24 and 72 hours after intercourse, the level of effectiveness drops to 89 percent.
The morning-after pill is not as effective in preventing unwanted pregnancy as other forms of contraception. As Options for Sexual Health explains, provided they are used properly, condoms are 98 percent effective, and the combined contraceptive pill yields a 99.7 percent effectiveness rate . Furthermore, the morning-after pill does not provide any protection against sexually transmitted diseases.