How does a pregnancy test work?

1) The wick of the pregnancy test is socked in urine. 2) The test contains mobile monoclonal antibodies with small coloured beads attached to them. 3) These mobile monoclonal antibodies only bind to hCG and this will form a hCG/antibody complex. 4) The urine moves up the test strip until it reached a window. 5) Here, there are immobilised monoclonal antibodies arranged in a line or pattern that only binds to the hCG/antibody complex. If the woman is pregnant, a coloured line or pattern appears in the first window. 6) The urine continues up the test strip to the second window. 7) Here, there is a line of immobilised monoclonal antibodies that only binds to the mobile monoclonal antibodies, regardless of whether they are bound to hCG or not. This coloured line forms irrespective of whether the woman is pregnant or not. It simply indicates that the test is working. Monoclonal antibodies: antibodies from a single clone of cells that are produced to target particular cells or chemicals in the body.