This test detects the level in the urine of the pregnancy hormone known as human chorionic gonadotropin (HCG).

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 after fertilization. After implantation of the fertilized egg, the levels of HCG rise rapidly in the first trimester and reach a peak 60 to 80 days after implantation. 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:

Because HCG is produced by the placenta, it is an indicator of pregnancy. HCG is produced regardless of whether implantation of the egg occurs within the uterus or outside of the uterus.

Most commonly, this test is performed to confirm or rule out pregnancy. Women of childbearing age who have not been using birth control while having intercourse should be screened with a quantitative HCG test if they are having the following symptoms:

How is the test performed?

The person supplies a urine sample. Ideally, this is from the first urination of the morning. This urine tends to be highly concentrated. The sample is sent to the lab and analyzed for the presence of HCG. The hormone is measured in terms of quantity per cubic centimeter of urine. The hormone is detected with a test that uses specialized antibodies. These substances clot with the HCG molecules. When this happens, the test is deemed positive. It is this reaction that makes the test strip turn color in over-the-counter pregnancy tests.