Do Low hCG Levels in Early Pregnancy Mean Miscarriage?

Understanding hCG Levels

Girl having a blood test
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In most cases, women discover they are pregnant when a home pregnancy test turns positive. These tests detect a certain level of the pregnancy hormone, human chorionic gonadotropin, in urine. The hormone, usually referred to as hCG, is made by placental cells following implantation of an embryo and rises quickly in early pregnancy. In fact, it usually doubling approximately every two to three days.

 

To confirm a pregnancy, doctors will often order serial quantitative hCG blood tests to measure the amount of hCG being produced and ensure it is rising as it should. Blood tests used to detect hCG are more sensitive than urine tests, and can often confirm a pregnancy as early as 11 days after conception. 

hCG Test Results

When a doctor says that a woman’s hCG level is low after one quantitative hCG blood test, that usually means that the number of milli-international units (mIU) per milliliter (mL) of blood is lower than the normal range of hCG for the number of weeks since the woman’s last menstrual period.

In early pregnancy, one low hCG result is not necessarily a cause for concern; normal hCG levels vary dramatically from person to person. When hCG levels are rising too slowly or dropping over time, however, this could be a symptom of miscarriage or other pregnancy complications.

A single low hCG result on a blood test is not enough to diagnose a miscarriage in early pregnancy, unless the low hCG level follows an earlier, higher hCG level.

Usually, if a doctor believes that a single hCG result is low, the doctor will order another one in two to three days to check the hCG doubling time.

If hCG levels decrease between two or more hCG tests, that is usually indicative of an impending miscarriage. 

Normal hCG Levels

hCG levels vary tremendously from woman to woman, and from pregnancy to pregnancy.

That is why the trend between two or more hCG blood tests yields much greater information about a pregnancy than any single number. 

However, the following ranges provide an overview of the amount of hCG produced by typical pregnancies. 

Weeks From Last Menstrual PeriodhCG Level (in mIU/ml)
35 to 50
45 to 426
518 to 7,340 
61,080 to 56,500
7-87,6590 to 229,000
9-1225,700 to 288,000
13-1613,300 to 254,000
17-244,060 to 165,400
25-403,640 to 117,000

hCG Levels in Later Pregnancy

While hCG levels rise rapidly in early pregnancy, and are therefore a good marker of the health of a pregnancy, they tend to level off as a pregnancy progresses. In the second or third trimester, most doctors do not use hCG levels to evaluate the progress of a pregnancy (however hCG levels may be checked as part of a prenatal screening test known as the alpha fetoprotein test, or AFP, which looks for abnormalities in the fetus).

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Sources:

American Pregnancy Association, "Human Chorionic Gonadotropin (hCG): The Pregnancy Hormone." July 2007. Accessed 17 Jan 2008.

Barnhardt, Kurt T., Mary D. Sammel, Paolo F. Rinaudo, Lan Zhou, Amy C. Hummel, and Wensheng Guo, "Symptomatic Patients With an Early Viable Intrauterine Pregnancy." Obstetrics & Gynecology 2004. Accessed 14 Jan 2008.

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