Serum Pregnancy Test
Alternate Names : Quantitative Pregnancy Test, Blood, HCG Quantitative Serum Test, Human Chorionic Gonadotropin Level Blood Test, Quantitative Serum Beta-HCG, Quantitative Beta HCG, Serum
This is a test that measures the exact amount of the pregnancy hormone, human chorionic gonadotropin (HCG), in the bloodstream.
Who is a candidate for the test?
HCG is a hormone that is produced by the placenta. It is detectable in the blood and urine within 10 days of fertilization. After the fertilized egg implants, or attaches, to the inside of the uterus or other structure inside the mother, the levels of HCG rise rapidly. The levels continue to increase throughout the first trimester of pregnancy and reach a peak 60 to 80 days after the fertilized egg implants.
HCG is thought to be important in converting the normal corpus luteum into the corpus luteum of pregnancy. The corpus luteum is a hormone-secreting structure that grows on the surface of the ovary after ovulation takes place.
In pregnancy, functions of the corpus luteum include:
promoting the growth of the fetus through the 12th week of pregnancy.
stimulating the development of fetal sex organs.
promoting the synthesis of male hormones by the fetal testes. Interestingly, an elevated level of HCG in men may indicate the presence of a testicular tumor.
Because HCG is produced by the placenta, the presence of HCG in a woman's blood indicates that she is most probably pregnant. HCG is produced regardless of the site of implantation of the egg in pregnancy. Usually this occurs within the uterus, but may happen outside the uterus, which is called an ectopic pregnancy. HCG may also be a sign of other conditions discussed below.
This test may be done to confirm or rule out pregnancy. Women of childbearing age who have been having sex should be screened with some type of HCG test if they are having the following symptoms:
delayed menstrual period
irregular spotting or bleeding
nausea or vomiting
There are two different tests to measure HCG. The other test is called a qualitative test. This can only give a "yes" or "no" answer as to whether or not HCG is present. This test is part of most home pregnancy test kits. The quantitative test gives a "yes" or "no" answer and gives the exact level of HCG in the blood. The quantitative beta HCG measurement can help give a rough estimate of the age of the fetus. It can also help determine if the pregnancy is progressing normally. Levels that are abnormally low or high may be signs that an abnormal medical condition is present. This would suggest the need for further evaluation and testing. The qualitative test is not able to provide this extra information.
How is the test performed?
A blood sample is taken from a vein on the forearm or hand. First, the skin over the vein is cleaned with an antiseptic. Next, a strong rubber tube, or "tourniquet," is wrapped around the upper arm. This enlarges the veins in the lower arm by restricting blood flow through them. A fine needle is gently inserted into a vein, and the tourniquet is removed. Blood flows from the vein through the needle, and is collected in a syringe or vial. After the needle is withdrawn, the puncture site is covered with a bandage for a short time to prevent bleeding. This blood is sent to the lab to determine the amount of HCG that is circulating in the blood. HCG is measured as a certain quantity per cubic centimeter of blood.