What is human chorionic gonadotrophin?

Human chorionic gonadotrophin (hCG) is a hormone produced by the placenta during pregnancy. Its sometimes called the pregnancy hormone because of its unique role in supporting a pregnancy. HCG is found in your urine or blood around 10 to 11 days after conception (when a sperm fertilizes an egg). Your hCG levels are the highest towards the end of the first trimester (10 weeks of pregnancy), then decline for the rest of your pregnancy. Healthcare providers measure hCG to confirm a pregnancy and provide details on how the pregnancy is progressing.

After conception occurs, a fertilized egg travels through your fallopian tubes to your uterus. The fertilized egg (called an embryo) implants (attaches) into the wall of your uterus. This triggers the placenta to form. Your placenta begins producing and releasing hCG into your blood and urine. HCG can be found in a persons blood around 11 days after conception. It takes slightly longer for hCG to register on urine tests.

HCG increases quickly (almost doubling every three days) for the first eight to 10 weeks of pregnancy. Healthcare providers look at how quickly a persons hCG levels rise in early pregnancy to determine how the pregnancy and fetus are developing.

Once your placenta begins making hCG, it triggers your body to create more estrogen and progesterone. Together with hCG, these hormones help thicken your uterine lining and tell your body to stop menstruating (or releasing eggs). The correct balance of these three hormones sustains and supports the pregnancy.

This chart shows how your hCG levels rise quickly and steadily in the first trimester before declining:

These numbers should be used as a guide only. Your levels may rise differently. Its not the number that matters as much as how the number changes. Your healthcare provider will let you know if your hCG levels need to be checked and what your test results mean for your pregnancy. Remember that healthy pregnancies may have lower than average hCG levels.

HCG can be detected in either blood or urine. However, a blood test is more accurate because it can detect smaller amounts of hCG.

There are two different types of blood tests to detect hCG:

An at-home pregnancy test will be positive if hCG is detected in your urine. A urine hCG test is performed by either peeing on a chemical strip or placing a drop of urine on a chemical strip. At-home urine tests typically require higher hCG levels to return a positive.

Keep in mind a low hCG level doesnt diagnose anything. Its a tool to detect potential issues. If your healthcare provider is concerned about your hCG level, they will test your levels again in two or three days. Then, they will compare the results to get a better picture of whats going on with your pregnancy.

HCG levels are typically not checked more than once or twice during pregnancy. Healthcare providers check hCG levels in the first trimester but usually dont need to check again. If initial hCG levels are lower than average, your provider will test hCG levels again in a few days. Assessing hCG levels is done sequentially, testing several days apart and comparing levels. Some prenatal genetic tests use hCG levels to check for the possibility of a fetus having a congenital disorder.

All people have small amounts of hCG in their bodies (almost undetectable levels). Your hCG levels rise fast and peak around 10 weeks of pregnancy. After that, they fall gradually until childbirth. In rare cases, germ cell tumors or other cancers may cause your body to produce hCG.

A low or declining hCG level may mean several things:

If your hCG level is low for the gestational age of the pregnancy, your healthcare provider will recheck your hCG levels in two or three days or perform an ultrasound to get a better look at your uterus.

High levels of hCG could indicate:

HCG injections can increase your chances of becoming pregnant when used with IVF (in-vitro fertilization) or IUI (intrauterine insemination). It works by inducing ovulation (when ovaries release an egg).

If you have a history of infertility, monitoring hCG levels early in pregnancy can help healthcare providers determine if a successful pregnancy has occurred.

HCG helps with the production of testosterone and sperm in people assigned male at birth (AMAB). Its also been used to treat undescended testicles in male infants.

Most of the time, youre unaware of your hCG levels other than when you take an at-home pregnancy test. Your healthcare provider may tell you your hCG levels are low based on the gestational age of the pregnancy. Obstetricians typically check hCG early on in pregnancy but dont continue to check it unless there are signs of problems. If your healthcare provider is concerned about how your pregnancy is progressing, they will recheck hCG levels and perform other diagnostic tests like ultrasound.

A note from Cleveland Clinic

Human chorionic gonadotropin (hCG) is known as the pregnancy hormone. Its claim to fame is that its the hormone at-home pregnancy tests check for. Your body produces a lot of hCG during the first trimester to support your growing baby. Your hCG levels provide valuable insight into your pregnancy and may alert your obstetrician to potential issues. However, if your pregnancy is going well, chances are you wont ever know what your hCG levels are. Contact your healthcare provider if you have questions about your hCG levels or what they mean.

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Human Chorionic Gonadotropin: Hormone, Purpose & Levels - Cleveland Clinic

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