Different Types of Pregnancy Tests
There are two basic categories of pregnancy tests – blood tests and urine tests. Both categories of tests look for the presence of human chorionic gonadotropin or hCG – a hormone that’s only produced in a woman's body when she’s pregnant.
A pregnancy test can look at not only the presence of hCG, but also the amount. In a healthy pregnancy, the level of hCG doubles every two to three days. If the levels are not doubling as expected, the pregnancy may not survive or, if the levels are rising more rapidly than expected, the mother may have a multiple pregnancy. Blood tests are more frequently used to determine the amount of hCG present because they provide quick results and the blood samples are often needed for other testing purposes as well. Home urine tests only look for the presence of hCG – a urine test for the amount of hCG must be ordered through a laboratory.
Home pregnancy tests consist of a plastic tube-shaped housing which contains absorbent material that’s filled with certain enzymes. These enzymes react in the presence of urine and in the presence of hCG. Typically, the presence of urine causes the control line to appear; this helps you know that you did the test properly and that the test is working. If hCG is present in your urine, a second line or symbol will appear as the enzyme reacts to the hCG. This second line may be parallel to the first line or at a right angle to it, forming a plus sign. It may be in a separate window or in the same window, and in some tests; the enzyme triggers a digital display that either reads “pregnant” or “not pregnant”.
Pregnancy tests vary in their ability to detect hCG at very small levels. This is directly related to the various products claims of how early their tests can detect pregnancy. According to a recent medical study, about 90% of the tests studied were able to detect pregnancy within one day after the woman's first missed period.
While many tests can detect hCG at low levels, a negative test results before your missed period may be a false negative. In other words, you could be pregnant, but you may not yet be producing enough hCG for it to register on the test. If your period doesn’t begin after taking the test, try testing again after several days.
To ensure maximum amounts of hCG in your urine, use your first morning urine for testing, or hold your urine for a period of about 4 hours before testing. Most tests ask you to use a midstream urine sample. This means that when you go the bathroom, you release a small amount of urine first and allow it to continue into the toilet. The next urine is either caught in a clean cup or directed toward the absorbent end of the test. In either event, the absorbent tip should be completely saturated with urine. Always follow the manufacturer's directions for more thorough details.
Also follow the manufacturer's directions when it comes to reading the test. Most tests have a time frame during which the results are accurate, and tests read either before or after the appropriate period can give an inaccurate result.
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