A pregnancy blood test is typically taken when a women experiences early pregnancy symptoms. For this type of test, a sample of blood is drawn from the patient using a needle and syringe. A laboratory technician will prepare a slide of the blood sample and examine it thoroughly under a microscope. The technician will proceed to analyze the sample to check for levels of a hormone called human chorionic gonadotropin (HCG).
HCG is present in a human embryo in the earliest stages of development. This pregnancy hormone will not be found in women who aren't pregnant. While urine tests can also show whether HCG is present, this is where the similarity of these methods end. With an at-home urine test, it is recommended to wait until a missed menstrual period—a blood test can be conducted sooner. This is because urine tests cannot detect levels of HCG at the earliest signs of pregnancy.
A pregnancy blood test, or serum test as it is alternately called, can detect the critical levels of the pregnancy hormone a week or so after a woman has ovulated. A woman who is experiencing symptoms of pregnancy may opt to take one of two specialized blood tests. She can either take the quantitative blood test for an accurate reading of exact measures of HCG or a qualitative blood test. The latter will merely provide conclusive results of whether or not the woman is pregnant.
Many doctors believe that a pregnancy blood test will show more accurate results than tests done at home. Although this may be the case, it is not a foolproof method, and cases can occur that show incorrect results. This is why it is often recommended to take the test more than once, especially if the initial pregnancy blood test was done very early on.
A pregnancy blood test cannot be done at home. This type of testing needs to be conducted by a medical professional. The laboratory results will typically take several days. These blood tests are more costly than the urine test or in-home pregnancy test.
If a blood test shows abnormally high levels of HCG, it can indicate serious complications or illnesses. This may also indicate the possibility the individual is pregnant with twins. Abnormally low concentrations of HCG in the blood might mean the woman is in danger of a miscarriage or the embryo is experiencing complications.