The test paper test is more accurate 20 days after intercourse. Under normal circumstances, semen ejaculated into the vagina, will pass through the cervical canal uterine cavity into the fallopian tube cavity, if it happens to meet the egg, it will be in the fallopian tube and the egg surface contact to form a zona pellucida reaction, and then through the zona pellucida and the egg envelope contact and fusion to complete the fertilization, the process is generally not more than 24 hours. This process usually takes less than 24 hours. 30 hours after fertilization, the egg starts to divide and the early blastocysts enter the uterine cavity on the 4th day after fertilization. On the 5th to 6th day after fertilization, the zona pellucida of the early blastocysts disappears and the late blastocysts are formed, and the egg will be deposited about 6 to 7 days after fertilization. HCG can be detected in the peripheral blood 1 day after the fertilized egg has been laid, if the blastocyst develops normally, it will rise twice as much in the following 1.7~2 days. 20 days after intercourse, the HCG value in the blood is already very high, which can be clearly detected by using the early pregnancy test paper, and it will show a positive or weakly positive result if you are already pregnant, and a negative result if you are not pregnant. You should choose morning urine when using early pregnancy test 20 days after intercourse, and if you are not completely sure, you can go to the hospital for examination.