Pregnancy test results need to be interpreted within five minutes, if a bar appears within five minutes, suggesting that may not be pregnant, if two bars suggest that may be pregnant, the next day two bars are not valid. Pregnancy tests are used to determine whether a woman is pregnant by detecting human chorionic gonadotropin, or HCG, in her urine. If there are two bars, the test is positive and she may be pregnant; if there is one bar, the test is negative and she is not pregnant. The results need to be read within five minutes, and if two bars appear the next day, they are invalid and cannot be used as a basis for the results. And the pregnancy test paper is not 100% accurate, if the result of the paper is negative, but still suspect that they are pregnant, can be under the guidance of the doctor to draw blood to test HCG or ultrasound test.