Home pregnancy test. Packet containing two 'Clear Blue' pregnancy tests. The tests work by detecting the hormone human chorionic gonadotropin (hCG) that is present in the urine of a pregnant woman. A dipper with an absorbent end is placed in the urine stream, or dipped in a urine sample. Blue lines display the results after one minute. A round window gives a reference line that shows that the test has worked. A line in a square window confirms the presence or absence of hCG. HCG is produced by the placenta, the organ that attaches an embryo to the wall of the uterus.