1. The principle of detecting pregnancy within a few days after intercourse. To detect pregnancy within a few days after intercourse, one needs to understand the process of human conception. During a woman\’s ovulation, eggs are released from the ovaries and travel through the fallopian tubes. If a sperm combines with an egg at this time, conception may occur. After fertilization, the egg will begin to divide and move to the endometrium to implant. This process generally takes 6-10 days. 2. Pregnancy test can be performed a few days after intercourse 1. Principle of pregnancy test The pregnancy test is to detect the presence of human chorionic villi (hCG) in urine or blood.