Interpreting hCG Levels in Early Pregnancy

Answers to Common Questions like Why Multiple Blood hCG Tests May Be Ordered

In early pregnancy, doctors may use two or more consecutive blood tests of the pregnancy hormone hCG (human chorionic gonadotropin) to find clues about how the pregnancy is progressing. Since, hCG is made by the placenta, a level that is decreasing or lower than expected may indicate pregnancy loss. 

That being said, early pregnancy hCG levels can be confusing to interpret, and answers to common questions are often different for each individual pregnancy. Let's address these questions here, so you are informed and can feel at ease with the tests your doctor is ordering. 

What Is hCG?

Pregnant woman with hands on stomach, mid section
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Human chorionic gonadotropin, or hCG, is a hormone produced by the placenta during pregnancy. Checking levels of hCG can give doctors information on how a pregnancy is progressing, although they are not reliable enough to date a pregnancy (they vary too widely).

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What Are Quantitative hCG Blood Tests?

Quantitative hCG blood tests measure the levels of hCG in a woman's blood. On the other hand, a qualitative hCG detects if hCG is simply present in the blood. 

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What Are Normal Levels Of hCG By Week Of Pregnancy?

Levels of hCG in the blood can vary, and a wide range of levels can be considered normal in early pregnancy. This is why one hCG measurement usually does not provide much helpful information for women with miscarriage symptoms. Instead, you need at least two tests to check whether the level is increasing or decreasing—a change in the level is what is key. 

In addition, research shows that a number of factors may affect hCG levels like a woman's body mass index, whether she smokes, the gender of the baby, the weight of the placenta, and whether hyperemesis gravidum symptoms are present. 

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Why Do Doctors Check hCG Doubling Times, And What's Considered Normal?

According to the American Pregnancy Association, in 85 percent of normal pregnancies, the hCG level should double every two to three days in the early weeks of pregnancy.

This is why doctors usually check two consecutive hCG blood tests (about two to three days apart) to check whether the hCG level is increasing or decreasing. 

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Should I Worry About Slow Rising hCG Levels?

Slowly rising hCG levels may or may not be a sign of pregnancy complications. Keep in mind that if 85 percent of normal pregnancies have hCG levels that double every two to three days, 15 percent of normal pregnancies might have slower doubling times.

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Do Low hCG Levels Mean Miscarriage?

The answer depends. One low hCG level does not necessarily mean much, especially if the low hCG level was in the first few weeks of pregnancy. Doctors really need two hCG results to determine whether an hCG level indicates miscarriage. The main indicator is whether the hCG level is going up significantly or not.

Also, it's important to understand that in addition to measuring hCG levels in early pregnancy, ultrasound exams and an assessment of your symptoms are also used to determine whether a miscarriage has occurred or is likely to occur. 

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Can Drinking Too Much Water Cause Low hCG Levels?

Your water intake should not affect the concentration of hCG in your blood, but drinking a lot of water could affect the accuracy of urine-based home pregnancy tests in the very early weeks of pregnancy.

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Should I Worry About High hCG Levels?

Many women worry about higher or lower than average hCG levels, but individual levels usually don't mean anything.

That being said, having a trend toward higher hCG levels can be normal or can be a sign of complications like molar pregnancy.

Sources:

American College of Obstetricians and Gynecologists. (August 2015). Frequently Asked Questions: Early Pregnancy Loss. 

American Pregnancy Association. (2017). Human Chorionic Gonadotropin (HCG): The Pregnancy Hormone.

Korevaar T et al. Reference ranges and determinants of total hCG levels during pregnancy: the Generation R study. Eur J Epidemiol. 2015;30(9):1057-66.

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