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Pregnancy
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How does a pregnancy test work
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.
How accurate is a home pregnancy test?
A. Although most manufacturers claim 99 percent accuracy in laboratory tests, inaccurate pregnancy test results may be more frequent in actual use, due to such factors as improper use of the pregnancy test, using a product past its expiration date, exposure of the test to the sun, and cancers. The procedures outlined in the instructions must be followed exactly for the pregnancy test result to be accurate.
Whatever the pregnancy test result or the brand used, it is recommended that you repeat the process a few days later to confirm the results because after conception, a woman produces a minimal amount of HCG. The strength of each pregnancy test varies, and although a woman may be pregnant, the test may not pick up the amount of HCG hormone present during the first pregnancy test.
Related topics to be discussed on the next chapter are:
pregnancy
teen pregnancy
pregnancy symptoms
early pregnancy
pregnancy calendar
pregnancy week
ectopic pregnancy
pregnancy calculator
pregnancy due date
stages of pregnancy
unwanted pregnancy |
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