Human Chorionic Gonadotropin (hCG)

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Test Overview

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 is made by the placenta during pregnancy.

HCG may also be made abnormally by certain tumors, especially those that come from an egg or sperm (germ cell tumors). HCG levels are generally 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.

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), beta human chorionic gonadotropin (beta-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. The integrated test uses an ultrasound measurement of the thickness of the skin at the back of the baby's neck (nuchal translucency) and the levels of free beta-hCG and a protein called pregnancy-associated plasma protein A (PAPP-A). The sensitivity of this screening test is about the same as that of the second-trimester maternal serum quad screening.¹

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

Routine pregnancy testing is usually done on a urine sample. The test does not measure the exact amount of hCG, but it shows if hCG is above the normal, nonpregnant level. Home pregnancy tests that show hCG in urine are also widely available.

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Last updated:	May 29, 2006
Author:	Jan Nissl, RN, BS
Reviewed By:	Renée M. Crichlow, MD - Family Medicine, Siobhan M. Dolan, MD, MPH - Reproductive Genetics
Editors:	Susan Van Houten, RN, BSN, MBA, Tracy Landauer