How Home Pregnancy Tests Work
Most over-the-counter home pregnancy tests are accurate 95 to 99 percent of the time—but the accuracy depends on your ability to perform the test as precisely as possible. The more opportunities for making mistakes, the greater the chance that your results will be affected.
Home pregnancy tests determine whether or not you are pregnant based on the detection of the pregnancy hormone human chorionic gonadotrophin (hCG), which is released by the placenta and can be detected in a pregnant woman's urine. Generally, your body makes 25 miu (milli-international units) of hCG about 10 days after conception. If the test you take is geared to detect a hormone level higher than what your body has produced, it may give you a false negative. Your test results can also be affected if you are taking certain medications—such as Pregnyl, Profasi, Pergonal, Humegon—that contain the pregnancy hormone.
To help make your test as accurate as possible, be sure to follow the test manufacturer's directions closely and conduct the test with clean hands. It is usually recommended to sample your first morning urine for optimal results.
Even though these "do-it-yourself" pregnancy tests are quite accurate, you should still have a blood test to confirm a positive test result. After all, you want to be absolutely sure that the good news is, in fact, true. And if your home pregnancy test comes back negative, don't despair. Sometimes a test done early in your cycle can produce a false negative. It's worth waiting a few days and trying again. Who knows, you may be pleasantly surprised!