Human Chorionic Gonadotropin (HCG)
HCG blood tests can be used to see if hCG is present but they can also measure the exact amount of hCG in the blood. A blood test can be used to see if a woman is pregnant, to check for abnormal pregnancies, or to test for hCG related to certain cancers.
The level of hCG in the blood is often used as part of a screening for birth defects in a maternal serum triple or quadruple screening test. Generally done between 15 and 20 weeks, these tests check the levels of three or four substances in a pregnant woman's blood. The triple screen checks alpha-fetoprotein (AFP), human chorionic gonadotropin (hCG), and a type of estrogen (unconjugated estriol, or uE3). The quad screen checks these substances and the level of the hormone inhibin A. The levels of these substances-along with a woman's age and other factors-help the doctor estimate the chance that the baby may have certain problems or birth defects.
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In some cases a combination of screening tests is done in the first trimester to look for Down syndrome. This screening test uses an ultrasound measurement of the thickness of the skin at the back of the fetus's neck (nuchal translucency), plus a blood test of the levels of the pregnancy hormone hCG and a protein called pregnancy-associated plasma protein A (PAPP-A). This test is about as accurate as the second-trimester maternal serum quad screening.1
HCG urine tests
HCG urine tests are usually used for routine pregnancy testing. The test does not measure the exact amount of hCG, but it shows if hCG is present. Home pregnancy tests that show hCG in urine are also widely available.
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Why It Is Done
A test for human chorionic gonadotropin (hCG) is done to:
- See whether you are pregnant.
- Find an ectopic pregnancy.
- Find and check the treatment of a molar pregnancy.
- See whether there is an increased chance of birth defects such as Down syndrome. The test is used in combination with other screening tests.
- Find and check the treatment of a cancer that develops from an egg or sperm (germ cell cancer), such as cancer of the ovaries or testicles. In such cases, a test for alpha-fetoprotein may be done along with a test for hCG.