The rapid test determines the concentration of the pregnancy-specific hormone human chorionic gonadotropin (hCG) in a woman's body. Its concentration increases after the conception of a child and becomes clinically significant from the 8-10th day after fertilization. The hCG level rises during the first trimester, reaching a maximum by 12-14 weeks. The more time has passed since conception, the easier it is to detect.
An express pregnancy test works on the same principle as a blood test for hCG. The only difference is that you don't have to donate blood. The test detects human chorionic gonadotropin in a woman's urine. There are two strips "hidden" in it. The first is always visible, the second - only if the woman is pregnant. The second strip contains an indicator that reacts with hCG. If a reaction has occurred, the strip becomes visible. If not, it remains invisible. No magic, just science.
Thus, interpreting the test results is very simple: one strip - no pregnancy, two strips - there is a pregnancy.