Normally, a woman’s pregnancy will not be detected 3 days after intercourse. This condition may occur because the test paper or blood hCG test is wrong, or because the woman also had sex before this intercourse. Usually the blood HCG will be slightly reflected 7 days after the male sperm enters the female vagina and completes fertilization. The hCG in the female blood will increase significantly only 10-14 days after intercourse, and thus the early pregnancy test will show a pregnancy result. Early pregnancy test paper and blood hCG test are not 100% accurate, for example, early pregnancy test paper may give wrong result due to user’s operation, and blood hCG may be elevated due to female estrogen level or disease factor. If you are indeed pregnant after 3 days of intercourse, it is possible that you are already pregnant at the time of this intercourse. It is recommended to review the vaginal ultrasound around 35 days of pregnancy to rule out the possibility of ectopic pregnancy. During pregnancy, you should pay attention to rest, do not overexert yourself, strengthen your diet and nutrition, and avoid sexual intercourse to avoid causing miscarriage.