Home pregnancy tests are, when the instructions are followed, generally 90% or more accurate at predicting pregnancy. However, there are several things that can cause a pregnancy test to show a positive result when you are not, in fact, pregnant. One of the “false positives” can be the occurrence of evaporation lines.

Evaporation lines are created on a pregnancy test as the urine stream crosses the test. The urine on the test sometimes evaporates, and leaves a mark on the test results area. This typically show up as a faint, grey or even colorless line in the test area. It is easy to mistake this line as a positive result when you may not actually be pregnant. No particular brand of home pregnancy test is immune to evaporation lines, although some home pregnancy tests may be better than others at avoiding these.

Be certain to read carefully the instructions that come with your home pregnancy test. Often, evaporation lines do not show up within the short amount of time that the test requires to indicate pregnancy. If a pregnancy test shows what you believe to be a positive result after the specified amount of time, the result may not be reliable, and you should test again in a few days or a week. Also, some tests will provide you with a symbol, such as a plus or minus symbol, that will indicate pregnancy, rather than a line.

Posted in Pregnancy

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