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Pregnancy
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Baby Pudge Won't Budge
Baby Pudge Won't Budge
How does a pregnancy test work?
A. All pregnancy tests are based on the presence of a hormone, human chorionic gonadotropin (HCG), that the pregnant woman produces after conception. The first self tests of the 1970's used ring, or "tube agglutination," tests consisting of pre-packaged red blood cells to detect HCG in urine. A ring at the bottom of the tube indicated a positive result. Sensitive to movement and human error, ring pregnancy tests are now rarely used.
Today's brands, such as e.p.t. and First Response, contain monoclonal antibodies that detect minute traces of HCG. These antibodies are molecules coated with a substance that bonds to the pregnancy hormone, if it's present, to produce either a positive or negative result. (Each test manufacturer uses a different "trade secret" chemical formula for the bonding substance.) The user collects urine and combines it with the antibodies provided in the package. The pregnancy test is timed, and a color change indicates the result. |
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