Blood pregnancy tests often detect pregnancy earlier than home pregnancy tests, according to the American Pregnancy Association. This makes blood pregnancy tests an attractive pregnancy test option for many women, but this type of test is not for everyone. Women should learn the advantages and disadvantages of blood pregnancy tests when deciding which pregnancy test option to choose.
Function
The placenta begins producing the pregnancy hormone called human chorionic gonadotropin, or hCG, after a fertilized egg attaches to the lining of the uterus. This hormone increases rapidly in early pregnancy, and is responsible for many early pregnancy symptoms. Blood pregnancy tests work by detecting if this hormone is present in a woman's bloodstream.
Time Frame
Blood pregnancy tests can detect pregnancy as soon as seven to 12 days after conception. However, miscalculating the conception date and testing too soon causes a false-negative result. Women who receive a negative result from a blood pregnancy test should consider retaking the test in another week or two if they miss their period or have any other early pregnancy symptoms.
Types
A qualitative pregnancy blood test checks to see if hCG is present in the bloodstream, and offers a simple positive or negative result. The National Women's Health Information Center, a publication of the National Institutes of Health, notes that a qualitative test is about as accurate as a urine pregnancy test.
A quantitative pregnancy blood test, also called the beta hCG test, measures exactly how much hCG is present in the blood. This test is very accurate, but still can offer misleading results if taken too early.
Advantages
Blood pregnancy tests are more accurate than home pregnancy tests when taken before a missed period. Quantitative blood pregnancy tests also measure the concentration of the hCG hormone in the blood stream. These measurements help to diagnose molar pregnancies, ectopic pregnancies, those that will miscarry and is also used as part of a screening test for Down Syndrome, explains MedlinePlus.
Disadvantages
Unlike home pregnancy tests, blood pregnancy tests are done in a doctor's office or clinic. Women who may be overly emotional about the result of the test may prefer the privacy of their own home. Although some insurance companies cover the cost of blood pregnancy tests and doctor visits, some do not. People without insurance coverage may find the testing expensive, especially compared with the nominal costs of home pregnancy tests. It also takes longer to get the results of blood pregnancy tests.
