1. The basic principle of how long it takes to detect pregnancy using test paper 2. The correct use of test paper to test pregnancy 3. The accuracy and error range of test paper pregnancy test 4. Other common pregnancy detection methods 1. How long it takes to test pregnancy can be detected using test paper Basic Principle How long it takes to detect pregnancy using test strips is a question that many women who are preparing to become pregnant or are already pregnant are very concerned about. The test paper pregnancy test determines whether you are pregnant by detecting whether the urine contains chorionic villi (HCG). HCG is a hormone secreted by the embryo after the fertilized egg implants. It will gradually increase over time.