Human Chorionic Gonadotropin (hCG)

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The human chorionic gonadotropin (hCG) test is done to check for the hormone hCG in blood or urine. Some hCG tests measure the exact amount and some just check to see if the hormone is present. HCG is made by the placenta during pregnancy. The hCG test can be used to see if a woman is pregnant or as part of a screening test for birth defects.

HCG may also be made abnormally by certain tumors, especially those that come from an egg or sperm (germ cell tumors). HCG levels are often tested in a woman who may have abnormal tissue growing in her uterus, a molar pregnancy, or a cancer in the uterus (choriocarcinoma) rather than a normal pregnancy. Several hCG tests may be done after a miscarriage to be sure a molar pregnancy is not present. In a man, hCG levels may be measured to help see whether he has cancer of the testicles.

HCG in pregnancy

An egg is normally fertilized by a sperm cell in a fallopian tube. Within nine days after fertilization, the fertilized egg moves down the fallopian tube into the uterus and attaches (implants) to the uterine wall. Once the fertilized egg implants, the developing placenta begins releasing hCG into your blood. Some hCG also gets passed in your urine. HCG can be found in the blood before the first missed menstrual period, as early as six days after implantation.

HCG helps to maintain your pregnancy and affects the development of your baby (fetus). Levels of hCG increase steadily in the first 14 to 16 weeks following your last menstrual period (LMP), peak around the 14th week following your LMP, and then decrease gradually. The amount that hCG increases early in pregnancy can give information about your pregnancy and the health of your baby. Shortly after delivery, hCG can no longer be found in your blood.

More hCG is released in a multiple pregnancy, such as twins or triplets, than in a single pregnancy. Less hCG is released if the fertilized egg implants in a place other than the uterus, such as in a fallopian tube. This is called an ectopic pregnancy.

HCG blood tests

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, it can check for abnormal pregnancies or it can 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.

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

Should I have the maternal serum screening test (triple or quad screen)?

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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	Should I have the maternal serum triple or quadruple test (triple or quad screen)?

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.

If a blood sample is collected, you do not need to do anything before you have this test.

If a urine test is done, the first urine of the day is generally the best to use because it has the highest level of hCG. A urine sample collected at least four hours after the last urination will also have high amounts of hCG.

Human chorionic gonadotropin (hCG) may be measured in a sample of blood or urine.

Blood sample collection

The health professional will:

• Wrap an elastic band around your upper arm to stop the flow of blood. This makes the veins below the band larger so it is easier to put a needle into the vein.
• Clean the needle site with alcohol.
• Put the needle into the vein. If the needle is not placed correctly or if the vein collapses, more than one needle stick may be needed.
• Attach a tube to the needle to fill it with blood.
• Remove the band from your arm when enough blood is collected.
• Put a gauze pad or cotton ball over the needle site as the needle is removed.
• Put pressure to the site and then a bandage.

Urine collection

If possible, collect a sample from the first urine of the day (this urine generally has the highest level of hCG). A urine sample collected at least four hours after the last urination will also have high amounts of hCG.

• Place the collection container into the stream of urine and collect about 4 Tbsp (59.15 mL) of urine.
• Do not touch the rim of the container to your genital area, and do not get toilet paper, pubic hair, stool (feces), blood, or other foreign matter in the urine sample.
• Finish urinating into the toilet or urinal.
• Carefully replace the lid on the container and return it to the lab. If you are collecting the urine at home and cannot get it to the lab in an hour, refrigerate it.

Blood test

The blood sample is taken from a vein in your arm. An elastic band is wrapped around your upper arm. It may feel tight. You may feel nothing at all from the needle, or you may feel a quick sting or pinch.

You may feel anxious while awaiting results of an hCG test done to check the health of your baby.

Urine test

There is normally no discomfort with collecting a urine sample.

Risks of a blood test

There is very little chance of a problem from having blood sample taken from a vein.

• You may get a small bruise at the site. You can lower the chance of bruising by keeping pressure on the site for several minutes.
• In rare cases, the vein may become swollen after the blood sample is taken. This problem is called phlebitis. A warm compress can be used several times a day to treat this.
• Ongoing bleeding can be a problem for people with bleeding disorders. Aspirin, warfarin (Coumadin), and other blood-thinning medicines can make bleeding more likely. If you have bleeding or clotting problems, or if you take blood-thinning medicine, tell your doctor before your blood sample is taken.

Urine test

There is no chance for problems while collecting a urine sample.

The human chorionic gonadotropin (hCG) test is done to measure the amount of the hormone hCG in blood or urine to see whether a woman is pregnant. HCG may also be measured to see whether cancer of the ovaries or testicles is present.

Normal

Normal values may vary from lab to lab.

High values

• If you are pregnant, very high levels of human chorionic gonadotropin (hCG) can mean a multiple pregnancy (such as twins or triplets), a molar pregnancy, Down syndrome, or that you are further along in an early pregnancy than estimated by your last menstrual period (LMP).
• In a man or a nonpregnant woman, a high hCG level can mean a tumor (cancerous or noncancerous) that develops from a sperm or egg cell (germ cell tumor), such as a tumor of the testicles or ovaries, is present. It may also mean some types of cancer, such as cancer of the stomach, pancreas, large intestine, liver, or lung.

Low values

• If you are pregnant, low levels of hCG can mean an ectopic pregnancy, death of your baby, or that you are not as far along in an early pregnancy as estimated by your last menstrual period (LMP).
• If you are pregnant, levels of hCG that are decreasing abnormally can mean a miscarriage (spontaneous abortion) is very likely.

Things that may affect the results of your test include:

• Doing a urine test for human chorionic gonadotropin (hCG) very early in pregnancy (during the first week after implantation) or on a urine sample taken in the middle of the day. The test may not always show an early pregnancy.
• HCG results may remain high (positive) for up to four weeks after a miscarriage (spontaneous abortion) or therapeutic abortion.
• Getting an injection of hCG to treat infertility. This may cause test results to appear high for several days after the injection.
• Having blood in the urine sample or soap in the collecting container, which may change the hCG level.
• Using diuretics and promethazine (such as Phenergan, Prorex, or Anergan). These medicines can cause false low hCG levels in urine test results.
• Using heparin, a medicine to prevent blood from clotting (anticoagulant)
• Using some medicines. These include hypnotics (such as Ambien), antipsychotics (such as Mellaril, Stelazine, and Serentil), and antinausea medicines (such as Compazine and Phenergan). Be sure to tell your doctor what medicines you take.

• Home pregnancy tests that find hCG in urine are widely available. For more information, see the medical test Home Pregnancy Tests.
• A blood test for hCG is generally more accurate than a urine test. If pregnancy is suspected even after urine test results do not show a pregnancy (negative results), a blood test can be done, or another urine test should be repeated in a week.
• HCG results may remain high (positive) for up to four weeks after a miscarriage (spontaneous abortion) or therapeutic abortion.
• The level of hCG in the blood is often used 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. For more information about estriol and hCG, see the medical tests Alpha-Fetoprotein (AFP) in Blood, Estrogens, and Hormone Inhibin A.
• A normal hCG value does not rule out the possibility of a tumor in the uterus, ovaries, or testicles. HCG is only one part of an overall evaluation when a tumor is suspected.

Citations

1. American College of Obstetricians and Gynecologists (2007). Screening for fetal chromosomal abnormalities. ACOG Practice Bulletin No. 77. Obstetrics and Gynecology, 109(1): 217–227.