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.
- Pregnancy: Should I Have Screening Tests for Birth Defects?
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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Pregnancy: Should I Have Screening Tests for Birth Defects?
Why It Is Done
A test for human chorionic gonadotropin
(hCG) is done to:
- See whether you are pregnant.
an ectopic pregnancy.
- Find and check the treatment of a molar
- See whether there is an increased chance of birth defects such as
Down syndrome. The test is used in combination with other screening
- 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.