How long does it take for test strips to detect pregnancy (detailed explanation of the correct use of test strips to test pregnancy) Test strip pregnancy testing is a method used by many women to detect pregnancy, but many people are not clear about the correct use of test strips to test pregnancy. This article will explain in detail how long it takes for test strips to detect pregnancy from aspects such as the principle of test strips, correct use methods, result judgment, precautions, etc. The principle of test strips is to determine whether you are pregnant by checking urine. After pregnancy occurs, a woman\’s urine produces a hormone called human chorionic troponin.