How Is A Pregnancy Blood Test Performed?
What is a pregnancy blood test?
A pregnancy blood test or a pregnancy serum test is a test that measures the exact amount of the pregnancy hormone, human chorionic gonadotropin (hCG), in the bloodstream.
Human chorionic gonadotropin (hCG) is a hormone that is produced by the placenta. It is detectable in the blood and urine within 10 days of fertilization (1 to 2 days after implantation).
There are two different pregnancy blood tests to measure human chorionic gonadotropin (hCG).
# Qualitative Pregnancy Blood Test – This can only give a “yes” or “no” answer as to whether or not HCG is present. This test gives results similar to what urine based home pregnancy test kits do.
# Quantitative Pregnancy Blood Test – This test can actually measure the exact amount of hCG in the woman’s blood. This measurement can help give a rough estimate of the age of the fetus. It can also help determine if the pregnancy is progressing normally. The qualitative test, described above, is not able to provide this extra information.
How is the pregnancy blood test performed?
A blood sample will be drawn from a vein on the forearm or your hand. The technician who draws your blood will clean the site with anticeptic and then apply a tourniquet to your arm to enlarge the target vein. A fine needle is gently inserted into the vein, and the tourniquet removed. The blood will be collected in a syringe or vial. The blood sample is sent to the lab to determine the amount of HCG that is circulating in the blood. The time it takes to get the results from your pregnancy blood test will vary from lab to lab. Talk to your doctor to find out how long it will be until you will get your results.
What do the pregnancy blood test results mean?
A qualitative pregnancy blood test will show you what level of hCG is in your blood. A positive quantitative pregnancy test is 5 mIU HCG. This level is usually seen shortly after conception.
You may have the quantitative blood test done several times during your pregnancy if your doctor is concerned about how your pregnancy is progressing. hCG levels should double approximately every 2 days for the first four weeks of pregnancy and by 6 to 7 weeks gestation, the levels may take as long as 3 1/2 days to double. If the hCG levels don’t double like this, the pregnancy is often considered in trouble and your doctor will be able to discuss the potential issues with you..
The test may fail to detect human chorionic gonadotropin (hCG) even when a woman is pregnant if the test is done too early. It takes at least 7 days after fertilization for the test to become positive. In most cases, by the time a woman has missed her period, the test will be positive if she is pregnant.