The function of pregnancy test paper is to detect whether there is early pregnancy, usually about 15 days after sex can be used. After sex, if a woman ovulates near the time of ovulation, an egg is discharged, sperm enters the woman’s body, and after the sperm-egg union and fertilization, it travels to the endometrium and is implanted in the uterine lining, which secretes human chorionic gonadotropin at this time. Human chorionic gonadotropin can be detected in the blood at the earliest, with the prolongation of time, the value of the hormone continues to increase, and ultimately can be detected in the urine, generally more than 12-13 days from sex, more accurate and reliable is about 15 days after sex, the test is generally positive at this time is more obvious, but also be able to directly determine whether there is an early pregnancy, if the test is not a problem, you can also except the occurrence of early pregnancy. If there is no problem with the test, it can also be excluded that this sexual intercourse will not cause early pregnancy.