If a bar appears on the pregnancy test, but the pregnancy test is clinically confirmed, it may be due to the following reasons: 1. the pregnancy test is out of date, so the test is inaccurate; 2. too much water was drunk before the urine test, so the urine is diluted and a false negative result may appear; 3. it is too early to test the pregnancy and the HCG level in the urine has not yet reached the level that can make the pregnancy test appear positive. The HCG level in the urine has not yet reached a level that can make the pregnancy test appear positive, so a negative result will also occur. As the number of days of pregnancy increases, the level of HCG gradually increases, and the test will show a positive result again. Therefore, if a pregnancy test shows one bar, but the last test is pregnant, it is mainly due to the above mentioned reasons.