Why hCG Doubling Times Are Important in Early Pregnancy

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When your physician talks about hCG, they are referring to the hormone human chorionic gonadotropin, which the placenta produces during pregnancy. That's why it's often called "the pregnancy hormone." Pregnancy tests detect hCG in urine or blood. Only quantitative blood pregnancy tests can determine the amount of hCG hormone in the body, while urine tests (which are also called qualitative) simply read positive or negative for the presence of the hormone.

In early pregnancy, the levels of hCG in a pregnant person’s blood rise rapidly—doubling every two to three days. Monitoring hCG levels is one way doctors can gather information about a pregnancy.

Testing hCG Levels

A blood test can first detect hCG about 11 days after you conceive. A urine test, those pregnancy test sticks you buy at the drugstore, can detect hCG at around 12 to 14 days after conception. Note that not all physicians use blood tests to test for hCG levels, especially if there are no symptoms of concern. Some practitioners will use a transvaginal ultrasound to confirm pregnancy rather than blood tests.

As noted above, the two common types of hCG tests are a qualitative test, which detects the presence of the hormone in your urine or blood, and a quantitative test, also called a beta hCG test, which measures the amount in your blood. If qualitative blood testing is used, the measurement of hCG is in milli-international units per milliliter. An hCG level above 5 mIU/ml is a positive indicator of pregnancy (some tests can detect over 6 mlU/ml, others need over 20 mlU/ml).

Multiple beta hCG tests can be used to monitor hCG levels over time. A single qualitative 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. Also, 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.

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. The level of this hormone peaks during the first eight to 11 weeks of your pregnancy, then declines and levels off.

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. So, that means that about 15% of viable pregnancies may have slower hCG doubling times.

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

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

General Ranges of hCG Levels

As noted above, normal ranges will vary—the key is how your level changes over time, which requires two or more sequential tests. Expected hCG levels in the first trimester are as follows:

  • A level less than 5.0 mIU/ml is considered to be a negative pregnancy test.
  • 3 Weeks: 5 to 72 mIU/ml
  • 4 Weeks: 10 to 708 mIU/ml
  • 5 Weeks: 217 to 8,245 mIU/ml
  • 6 Weeks: 152 to 32,177 mIU/ml
  • 7 Weeks: 4,059 to 153,767 mIU/ml
  • 8 Weeks: 31,366 to 149,094 mIU/ml
  • 9 Weeks: 59,109 to 135,901 mIU/ml
  • 10 Weeks: 44,186 to 170,409 mIU/ml
  • 12 Weeks: 27,107 to 201,165 mIU/ml
  • 14 Weeks: 24,302 to 93,646 mIU/ml
  • 16 Weeks: 8,904 to 55,332 mIU/ml

Why Check hCG Doubling Times?

Doubling times for hCG are a good way to check whether a pregnancy is progressing normally until about six or seven weeks after your last menstrual period. However, in a low-risk pregnancy, as noted above, checking hCG doubling times is not usually indicated. More commonly, this is used when there are issues of concern (such as previous miscarriages) with the pregnancy.

After 5 to 6 weeks gestation, ultrasounds become the best tool for getting information on how the pregnancy is developing and are much more accurate than hCG numbers. Know that women with low numbers can go on to have normal pregnancies and healthy babies. Additionally, hCG levels are not an accurate way to date a pregnancy (that is, to determine conception and from there, an estimated due date).

Note that hCG levels and doubling times are not the only indicators that doctors use to diagnose a miscarriage. They will also look at any signs and symptoms you may be experiencing, such as vaginal bleeding, backache, and/or abdominal cramping when evaluating viability.

A Word From Verywell

Finding out that your hCG levels are atypical can be very stressful and upsetting. Still, know that a slower (or faster) hCG doubling time does not always indicate a miscarriage. However, as heartbreaking as it is to hear, sometimes it does. While it is very difficult to wait, the best course of action is usually to pursue further testing. If your pregnancy does end in miscarriage, take comfort that early pregnancy loss is not your fault and is very common—and usually does not indicate a problem with your fertility.

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  1. Korevaar TI, Steegers EA, de Rijke YB, et al. Reference ranges and determinants of total hCG levels during pregnancy: the Generation R StudyEur J Epidemiol. 2015;30(9):1057-1066. doi:10.1007/s10654-015-0039-0

  2. MedlinePlus. HCG blood test: quantitative. Reviewed September 25, 2018.

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