1. How long does it take to be pregnant with a test strip? 1.1 The principle of pregnancy test strip Pregnancy test strip is a method that uses the level of human chorionic villi (hCG) in urine to determine whether you are pregnant. hCG is a hormone secreted by the embryo after the fertilized egg implants, and its levels gradually increase as the pregnancy progresses. 1.2 Time for pregnancy test with test paper Generally speaking, around 6-12 days after pregnancy, the hCG level will reach a level that can be detected by the test paper.