The normal fertilization process requires the sperm to enter the vagina and some of the sperm to continue forward into the cervix and then reach the fallopian tubes to unite with the egg and eventually form a fertilized egg. Because of the short survival time and poor motility of sperm on the underwear outside the body, they do not usually pass through the underwear to unite with the egg, so there is no need to worry too much. It has been found that sperm survive outside the body for a very short period of time, only about 2 hours, and that sperm will only move forward in a suitable environment, such as with the action of enzymes in the vagina, so the sperm on the underwear outside the body have very little mobility and usually do not enter the vagina through the underwear and basically cannot unite with the egg. Even if the sperm is normally ejaculated into the vagina, the number of sperm that end up in the fallopian tubes is very small. If the couple has no desire to get pregnant, it is recommended to use good contraception, such as condoms. Although the chances of a fertilized egg forming after external ejaculation are small, there is no guarantee that pregnancy is not possible. If a woman with a normal menstrual cycle has a delayed period after intercourse, she can use a pregnancy test or go to the hospital for an HCG test, etc., to clarify whether she is pregnant.