How does a home pregnancy test work?

pregnancy test work

Testing for pregnancy is easier and less expensive than ever, thanks to the ready availability of home pregnancy tests. These tests are also more reliable than ever. However, you can still receive a false negative result if you use the test incorrectly. Here is a brief description of how today’s home pregnancy tests work, and advice on how to achieve the most accurate results.

Home pregnancy tests measure the amount of a hormone called human chorionic gonadotropin (commonly abbreviated as hCG) in the woman’s urine. Since this hormone is only produced by pregnant women, its presence in any amount in a woman’s urine means that the woman is indeed expecting a baby. While false positives are exceedingly unlikely with today’s home pregnancy tests, it is still quite possible to obtain a false negative result.

How can one avoid a false result?

Different brands of tests are formulated for detecting different levels of hCG, meaning that some tests are accurate earlier in the woman’s cycle than other tests that are calibrated to detect higher levels of hCG. Thus, testing too early after conception may mean that the woman’s hCG level is not yet high enough to be detected by that particular test. For this reason, it is important to read the instructions on the test and use it at the recommended time in your cycle using it too early not only results in a possible false negative but also wastes the money!

Another possible cause of a false negative test stems from the fact that different women produce hCG at varying levels in their cycle so even if you use the test at the recommended point in your cycle according to the test’s instructions, you may still obtain a false negative result. Test a few days later, if you have still not menstruated, or see your doctor for a more accurate test. (Even if you do get your period, it may be worth testing again the bleeding that sometimes occurs as a result of the fertilized egg implanting in the uterus may be confused for a regular period, especially if you are accustomed to light periods.)

As mentioned above, false positives are exceedingly rare so if a home pregnancy test indicates that you are pregnant, it is most likely correct. In this case, schedule a visit with your doctor to confirm the pregnancy, and act as if you are definitely pregnant: avoid substances and behaviors (such as alcohol, cigarettes, and drugs) that might endanger a developing fetus, and begin taking prenatal vitamins.

When shopping for a home pregnancy test, consider buying a pack of two or three tests in case you test negative the first time and need to retest a few days or a week later; it’s also a good idea to have extra tests on hand for future use. Also, if you are only one or two days past the day that you expected your period to begin, look for a test that works earlier in the menstrual cycle. Following these suggestions may cost a little more initially, but will save you money and worry in the long run (and may just produce more reliable results).

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