That is what I was wondering after I read that Halle Berry took 35 pregnancy tests before one of them showed up positive!  She says she believed she was pregnant, but the tests kept on coming up negative.

According to WebMD, “The home tests have similar results to the pregnancy tests done on urine in most health professionals’ offices if they are used exactly as instructed.” BabyHopes says they are about 97% accurate. Home pregnancy kits work by detecting levels of hCG, a hormone that is produced during pregnancy and released in the urine.

In the first few weeks of pregnancy, the amount of hCG in the urine rises very quickly, doubling every 2 to 3 days. This is why most tests are the most accurate after the first week of pregnancy. Before then, the levels of hCG might not be high enough to influence the test results. You can buy super-senstive tests that detect these levels right away, but be aware that 25% of pregnancies end in miscarriage, often very early.

For tips on how to get the best results from you at-home pregnancy test, read this article at BabyHopes.