There are two possibilities for a line to appear on a pregnancy test at night, one is that you are pregnant but not detected, and the other is that you are not pregnant. Because the pregnancy test needs to be based on the human chorionic gonadotropin in the urine to determine whether the pregnancy, and the accumulation of human chorionic gonadotropin in the urine has a lot to do with the time to hold the urine. If you hold your urine for too short a period of time, even if you are pregnant, it is very likely that you will not be able to detect it because the HCG concentration in your urine is too low. Therefore, when taking a pregnancy test, two conditions need to be met to ensure the accuracy of the test. One is that it needs to be more than 2 weeks after intercourse, because HCG in the urine will not be obvious if the time is too short. Another is to try to use the morning urine of the middle part of the urine when testing, can effectively ensure the accuracy of the test.