Blood pregnancy tests can come back with inconclusive results when the level of hormone is not at a detectable level. Such a result does not mean that the individual is not pregnant nor does it definitively mean that she is pregnant.
Blood pregnancy tests are often used to detect prenatal issues or complications, such as ectopic pregnancy. Other blood tests during pregnancy are used to test for diseases such as AIDS. All tests for pregnancy are based on the level of Human chorionic gonadotropin hormone (hCG) present. Blood tests for pregnancy, also known as serum tests, are not always done in the case of suspected normal pregnancy since traditional urine-based pregnancy tests are based on the same hormone. According to the American Pregnancy Association, there are exceptions to that rule; for example, if the urine test is done incorrectly and offers a negative result but there are still physical signs of pregnancy, a blood test can be performed in a doctor's office. Blood pregnancy tests are not sold in stores like urine pregnancy tests, which are sold in various pharmacies and markets.