Couples who are trying to get pregnant are are frequently confused about how pregnancy blood tests are performed and what they mean.
There are two main types of pregnancy tests – blood tests and urine tests. Both tests detect pregnancy by noticing a hormone called human chorionic gonadotropin (hCG) which is also commonly called the ‘pregnancy hormone’ because it is created soon after the embryo has attached itself to the uterine lining in the womb. This hormone is easily measurable in the blood and urine within 10 days of fertilization, or 1 to 2 days after implantation has occured.
There are two types of blood tests:
A quantitative blood test measures the exact amount of hCG in the blood. Based on the results, the age of the fetus can be approximated. Unlike the qualitative test, this test can tell if the pregnancy is developing normally.
A qualitative hCG blood test gives a simple yes or no answer to whether you are pregnant or not by simply detecting the presence of hCG in the blood. If you have not yet taken a home pregnancy test, then a qualitative blood test is usually recommended before a quantitative blood test.
How is the blood test conducted?
As with anything that relates to blood, it has to be drawn, before it can be analyzed. Although the blood is usually withdrawn from the forearm, if your veins like to play hide and seek, then the blood will be drawn from one of the veins on the back of your hand instead. A technician or nurse will first clean the area with an antiseptic, before applying a tourniquet to your arm to enlarge the vein. Very gently, a delicate needle is inserted into the vein, and then the nurse will remove the tourniquet. A syringe or vial is used to collect the blood. This sample will then be sent to the laboratory to determine how much hCG is in a woman’s blood. Each lab has its own turnaround time, so be sure to check with the nurse as to when the results can be expected.
If you live in a city, you might be able to go to a hospital, which is faster concerning lab results, should you be anxious to know what your results are.
Understanding the results
For basic qualitative blood tests, if the amount of hCG is over a certain limit it will come up as positive, especially if the level is at least 5 mIU hCG. This is most easily detected shortly after conception has taken place.
With the more complex, quantitative, pregnancy tests that relate to blood, the exact amount of the hormone in the blood is measured. A medical practitioner will then be able to determine how far along you are. This test will be repeated throughout the pregnancy to make sure that everything is progressing, as it should. During the first four weeks of your pregnancy, your hCG levels should double every two days. However, by 6 to 7 weeks gestation, your hCG levels may take as long as 3 1/2 days to actually double. If your hCG levels do not double properly, your pregnancy by at risk and your doctor will discuss any concerns with you.
Blood tests are not infallible as everything is prey to human error. If one is not sure about the result, have a second test done. Sometimes this occurs if the blood test is conducted too early.