Why hCG Doubling Times Are Important in Early Pregnancy

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When your physician talks about hCG, they are referring to human chorionic gonadotropin—"the pregnancy hormone" produced by the placenta.

The presence of hCG helps confirm pregnancy. But beyond that, levels of hCG can help doctors gather information about early pregnancy, including whether or not a miscarriage is occurring.

The levels of hCG in a pregnant person’s blood rise rapidly, doubling every two to three days. This is known as hCG doubling time. When this does not occur as expected, it could be cause for concern.

This concern does sometimes prove to be justified. However, women with low numbers can go on to have normal pregnancies and healthy babies.

Testing hCG Levels

The two most common tests for hCG levels differ not only in how they are done, but what they can reveal.

  • Qualitative test: This only detects the presence of the hormone (around 12 to 14 days after conception). A urine test—the pee-on-a-stick pregnancy test available at drugstores—is a qualitative test.
  • Quantitative test: This determines the actual amount of the hormone in the body by testing a blood sample. A quantitative test (a.k.a. a beta hCG test) can detect the hormone sooner, about 11 days after you conceive.

For a quantitative test, hCG is measured in milli-international units per milliliter (miU/ml). An hCG level above 5 mIU/ml is a positive indicator of pregnancy. Anything less than that is considered a negative pregnancy test.

While quantitative blood tests can be useful, not all physicians order them to confirm pregnancy. Some practitioners simply use a transvaginal ultrasound for this purpose.

Once pregnancy is confirmed, however, multiple beta hCG tests may be used to monitor hCG levels during early pregnancy. This is typically only done when there are issues of concern with the pregnancy, such as a history of miscarriage. It is not typically needed for low-risk pregnancies.

A single quantitative hCG test value does not provide much information, so these tests need to be repeated to see whether and how quickly hCG levels are increasing.

Typical hCG Doubling Times

In a typical pregnancy, your hCG levels double every 48 to 72 hours. This period increases to about every 96 hours as you get further along.

Levels peaks during the first eight to 11 weeks of pregnancy, then decline and plateau.

Expected hCG levels in the first trimester are as follows. However, know that there is a very wide range of normal hCG levels that are perfectly healthy.

The key is the rate at which the hormone is increasing in the blood, not how much you start out with.

 Weeks Pregnant  hCG Level
 3 5 to 72 mIU/ml
 4 10 to 708 mIU/ml
 5 217 to 8,245 mIU/ml
 6 152 to 32,177 mIU/ml
 7 4,059 to 153,767 mIU/ml
 8 31,366 to 149,094 mIU/ml
 9 59,109 to 135,901 mIU/ml
 10 44,186 to 170,409 mIU/ml
12 27,107 to 201,165 mIU/ml

What hCG Doubling Times Can Show

Checking hCG doubling times is a good way to monitor whether a pregnancy is progressing normally until about six or seven weeks after your last menstrual period.

After five to six weeks gestation, ultrasounds become the best tool for getting information on how the pregnancy is developing and are more accurate than hCG numbers.

Slow-rising hCG doubling times can be a sign of miscarriage or a symptom of ectopic pregnancy, but this is not always the case. The two- to three-day doubling guideline holds true in 85% of normal pregnancies. That means that about 15% of viable pregnancies may have slower hCG doubling times.

Your hCG levels and doubling times alone are not enough for your doctor to make one of these diagnoses. They will also consider any signs and symptoms you may be experiencing, such as vaginal bleeding, backache, and/or abdominal cramping when evaluating viability, as well as run additional tests.

High hCG levels also have meaning. High levels can indicate:

  • A miscalculated conception date
  • A molar pregnancy
  • A multiple pregnancy (twins or more)

Your hCG levels are not an accurate way to date a pregnancy (that is, to determine conception and from there, an estimated due date).

A Word From Verywell

Finding out that your hCG levels are atypical can be very stressful and upsetting. Know that a slower (or faster) hCG doubling time does not always indicate an issue with your pregnancy. However, as heartbreaking as it is to hear, sometimes it does.

While it can be very difficult to wait for more results, pursuing further testing is usually the best course of action. 

If you are diagnosed with an ectopic pregnancy or miscarriage, remind yourself that early pregnancy loss is not your fault and is very common—and it usually does not indicate a problem with your fertility.

9 Sources
Verywell Family uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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Additional Reading

By Krissi Danielsson
Krissi Danielsson, MD is a doctor of family medicine and an advocate for those who have experienced miscarriage.