It is also clinically accurate if you use early pregnancy test paper to test when you are about to have your period, even if you are already pregnant, you will not be able to detect it with early pregnancy test paper. Because the fertilized egg enters the uterine cavity and lays in the uterus during intercourse at the time of ovulation, the blood HCG is secreted only after it lays in the uterus, so the response is relatively late due to the value of HCG in the urine. When you are about to have your period, even if you are pregnant, you will not be able to detect it with the early pregnancy test. It is possible to detect pregnancy with the early pregnancy test about 20 days after having intercourse during ovulation. Therefore, it is accurate to use the early pregnancy test before you get your period, but it does not detect pregnancy.