The sperm is difficult to be completely discharged from the body. After ejaculation, the vagina can be flushed out with water in time, but there are still residues left in the body. If you are ovulating, there is a possibility of pregnancy, if you do not intend to get pregnant, it is recommended to take emergency contraceptive pills in time. Emergency contraceptive pills are generally effective when taken within 72 hours after the event, the earlier you take them, the better the effect, so it is recommended to take emergency contraceptive pills on time to prevent pregnancy. If you do not intend to get pregnant, it is recommended that you do a good job of contraception, you can use condoms, contraceptive rings, etc. It is best not to take birth control pills often, the side effects are very large, will cause endocrine disorders, often take also easy to affect future fertility, etc.