Taking birth control pills before sex is generally not effective. But it depends on which type of pill you are taking: if it is a short-acting pill, it can be effective as long as it is taken according to time. If you are taking the emergency contraceptive pill, then take it before sex, there is no contraceptive effect, the emergency contraceptive pill is usually taken within 72 hours after sex, but the earlier you take it, the better the effect, you can take the emergency contraceptive pill within one hour after sex, so the chances of contraceptive success are very high. If there is no intention to get pregnant, usually sexual life should still pay attention to good contraception to avoid causing unintended pregnancy. After taking the emergency contraceptive pill, vaginal bleeding will usually occur within 10 days, suggesting that the contraception is successful, if there is no vaginal bleeding, it does not necessarily mean that the contraception has failed.