Generally, you can use test strips to detect pregnancy after one week of intercourse, and the longer the time after intercourse, the higher the accuracy rate. Pregnancy test strips are a convenient and quick way to detect early pregnancy by testing the value of HCG, the human chorionic gonadotropin, to detect if you are pregnant. This hormone is produced by the placenta and usually appears in the urine after a few days of pregnancy, but due to the small amount, it is not easy to detect at first and only becomes increasingly evident around 10-14 days, so testing at this time can indicate pregnancy. However, it is important to note that although the early pregnancy test indicates that a woman can do a pregnancy self-test one day after missing her period, not all pregnant women emit HCG at the same rate and in the same amount, so a test taken too early may also show a false negative reaction. Usually, in the early stage of pregnancy, women will experience a series of early pregnancy reactions such as dizziness, nausea, drowsiness and breast swelling, which will disappear on their own after three months. If a woman experiences the above symptoms, she can use early pregnancy test paper and pregnancy test stick for preliminary pregnancy detection. However, clinically, both early pregnancy test and pregnancy test can only be used as the first step of pregnancy screening, but not as a confirmatory method. Therefore, in order to avoid ectopic pregnancy and to ensure the healthy development of the fetus, you should go to the hospital for further investigation.