A positive urine pregnancy test the first time and a negative urine pregnancy test the second time proves that one of the two tests was wrong. Urine pregnancy tests are not 100% accurate and have a false negative or false positive rate. This is mainly due to the fact that the urine pregnancy test is affected by a number of factors, such as the quality of the test strip used, the standardization of the test procedure, and the concentration of the patient’s urine, all of which can affect the results of the urine pregnancy test. When this happens, it is recommended that the patient go back to the regular drugstore to buy qualified pregnancy test strips, and then use the morning urine to continue the test, or the patient can go to the hospital to check the blood chorionic gonadotropin for confirmation.