If sperm is ejaculated into the vagina, pregnancy can be prevented by the following methods: 1. standing up immediately so that a large amount of semen is expelled from the vagina, or douching the vagina with a douche can also make most of the semen expelled from the vagina and reduce the chance of pregnancy, but clinically it does not achieve the goal of absolute non-pregnancy. 2. taking oral emergency contraceptive pills within 72 hours after intercourse to give contraception, emergency contraceptive pills can make the uterus The emergency contraceptive pill can make the endometrium thicken abnormally to prevent the fertilized egg from being laid, or it can clinically inhibit ovulation of the ovaries, which will also achieve the purpose of contraception. If you are not using contraception, you can do the above to prevent pregnancy, and it is better to use condoms during sex to prevent pregnancy.