As in urine pregnancy test, a blood pregnancy test also works by detecting the pregnancy hormone, hCG (human Chorionic Gonadotropin) presence in the blood sample. Blood tests can detect hCG earlier in a pregnancy compared to urine tests or home pregnancy tests. These tests can confirm a pregnancy about 8 to 10 days post ovulation. Blood pregnancy test can give a positive result when detect 5 mIU/ml (milli-International Units per milliliter) of hCG in the blood. This little amount of hCG is usually seen only shortly after conception.
Quantitative Blood Serum Test:
Quantitative blood serum test which also known as the beta hCG test can measure the exact amount of hCG hormone in the blood. This is a very accurate test because it can detect even trace amounts of hCG hormone. Generally hCG levels double approximately every 2 days for the first four weeks of pregnancy. A quantitative blood test not only helpful in confirming a pregnancy, but also can help assessing whether a pregnancy is progressing normally or not.
Qualitative Blood Serum Test:
Qualitative blood test can only confirm the presence of pregnancy hormone (hCG) in the blood and therefore whether a woman is pregnant or not. The accuracy of this test tends to be about as accurate as a home urine test.
How the Blood Pregnancy Test is Performed:
The test is done just like a typical blood test. The puncture site (mostly the forearm or the back of the hand) should be cleaned with an antiseptic. Usually a tourniquet will be placed around the upper arm to apply pressure on the blood stream. A sterile needle will then be inserted into the vein and the blood will be collected in an airtight vial or syringe. The blood sample will then be sent out to the lab to be analyzed.
Blood Test Results:
Blood tests that performed in a medical center or doctor’s site tend to have accuracy until 98 to 99 percent. You can conduct this test at 7 days after you ovulate (which is about one week before your period is due) and still give you an accurate result.
As with urine pregnancy test, blood pregnancy test also has possibility to get false results, both negative and positive.
- False negative results
This is the condition when you are actually pregnant but the test result is negative. This usually happens when the test was performed too early and there might not enough hCG amount in the blood yet to detect a pregnancy.
- False positive results
This is the condition when you are not pregnant but your test result is positive. This may occur if you are taking a medication that contains hCG.