A regular home pregnancy test is in the form of a dipstick that is placed in the urine stream. This detects the human chorionic gonadotropin, which is a hormone produced during pregnancy. The accuracy of the test depends on the production of this hormone. If the production is inadequate, then the test will show that you are not pregnant even if you are. This is called a false negative. If the production of hormone in the body is caused due to some other reason, it will show you that you are pregnant. This is called a false positive. There are various reason that can cause a false positve or negative. Once you have a positive result, it is adviced to contact a doctor for prenatal care. Here are all the reason why you can have a false positive.