How Accurate Are Home Pregnancy Tests

The morning after, one of your biggest questions is going to be how accurate are home pregnancy tests? Even if your partner in crime—whether she be a wife, girlfriend, friend or one night stand—might not the know the answer, either, and the instructions on home pregnancy tests aren’t always clear. To help you straighten out your future, here’s the lowdown on home pregnancy tests.

How They Work Home pregnancy tests work by detecting the hormone present during pregnancy. This hormone, commonly referred to as hCG, shows up in a woman’s urine when she is pregnant and while there are many brands of home pregnancy test, all work by testing the urine for this particular hormone. hCG shows up in most women six days after conception, or her egg implanting in the lining of her uterus. Because hCG nearly doubles in quantity every day a woman is pregnant, the further along she is the more effective the test will be.

Accuracy of Early Tests The companies that make home pregnancy tests want you to choose their brand so they make bold accuracy claims. This advertising can lead to misleading results so let’s get a few things straight. In general, home pregnancy tests have an accuracy rate of 99% or better, but only if it is taken six days after a missed period. Studies have confirmed that tests taken within two days of a missed period should not be relied on for accuracy because the level of hCG produced during early conception varies greatly between women. Even the pregnancy test that scored the highest only worked at an 95% success rate.

Reasons for Incorrect Results Even with a 99% accuracy rate when used six days after a missed period, there are still things that can trick a pregnancy test. For instance, a woman who has recently given birth, miscarried, or used fertility drugs will likely already have a high level of hCG in her system and the test might pick up on that and produce that little pink line.

For Best Results… So, with all this in mind, when is the best time to take a home pregnancy test? First of all, pick a highly sensitive home pregnancy test. You can do this by reading the insert in the package. Look for the brand that lists the lowest mIU concentration of hCG detectable. For example, a test that can identify hCG at 25 mIU will be more accurate than one that can detect it at 40 mIU.