Are Low hCG Levels a Sign of Miscarriage?

Abnormal hormone levels may suggest complications

Midwife taking blood sample from arm of pregnant woman Obstetric examination. Midwife taking a blood sample from the arm of a pregnant woman. Regular check- ups are necessary during pregnancy so that the development of the baby and the health of the mother can be monitored. Blood can be tested to provide information on the mother's nutrition, for example blood glucose levels, and levels of hormones and antibodies.
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Human chorionic gonadotropin (hCG) is a hormone produced during pregnancy. It is made by cells in the placenta and nourishes the egg after it has been fertilized and attaches to the wall of the uterus.

During the first trimester, levels of hCG are meant to increase significantly in the course of a normal pregnancy. Particularly in the first eight to 11 weeks, those levels can be expected to double every two to three days.

When this doesn't happen—or the hCG levels are dropping—a doctor will want to intervene to pinpoint why this is happening. One of the things that will be explored is whether these abnormalities are suggestive of a miscarriage.

How hCG Is Measured

Following conception, hCG can be detected in the blood in as early as 11 days. Detection is made using a test known as the quantitative serial beta-hCG assay which measures the volume of hCG in a milliliter of blood. A single hCG test may be used to see if your levels are within the normal range expected at that point in your pregnancy. A serial hCG, by contrast, is done to assess hCG doubling times.

With serial hCG measurements, quantitative hCG blood tests are drawn two to three days apart in line with expected rates of increase. By and large, serial testing provides more useful information than a single hCG level when evaluating a pregnancy.

Normal Trends in hCG Levels

A "normal" hCG level can vary enormously from woman to woman and from one pregnancy to the next.

Beyond the actual number, what doctors will really want to watch is how that those levels trend and whether they are increasing as expected.

The normal range and trending of hCG in an uncomplicated pregnancy would be as follows:

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

It is generally between weeks five and six that we see the first significant spike in hCG production. By six to seven weeks, levels will continue to double every three to four days, eventually reaching its peak sometime between weeks eight and 11.

Beyond this point, the hCG become less useful in monitoring pregnancy, and doctors will begin to turn to other tools (such as a transvaginal ultrasound) to determine the status of the pregnancy.

When hCG Trends Are Abnormal

In terms of miscarriage, it is the early days doctors are often most concerned about since pregnancy loss typically occurs during the first 13 weeks. It is at this stage that hCG monitoring provides one of the best means to assess the health and status of a pregnancy.

Concerns arise when one of three things happen: hCG levels are lower than expected, the rate of HCG increase is slower than expected, or hCG levels begin to drop.

Each may suggest the following complications:

  • A low hCG level can mean any number of things. In some cases, it may simply be that the pregnancy date was miscalculated, and you are not as far along as you had thought. Further testing would be needed to determine the cause, which may or may not include a miscarriage, a blighted ovum (where the egg has not attached to the uterus wall), or an ectopic pregnancy (where the egg implants outside of the uterus).
  • Slow-rising hCG levels may also be a sign of trouble in early pregnancy. Keep in mind, however, this occurs is around 15 percent of pregnancies that continue without complications. Further investigation and monitoring would need to be performed to check for possible causes.
  • Dropping hCG levels in the first trimester over the course of two to three days is usually the sign of an impending miscarriage. This is especially true for women experiencing symptoms of miscarriage such as heavy vaginal bleeding. Decreasing levels of hCG in the second and third trimester are usually not a concern.

It is also important to note that excessively high levels of hCG may be the indication of a multiple pregnancy (such as twins or triplets) or a molar pregnancy (resulting from a nonviable, fertilized egg).

As with a low hCG, a high hCG could simply be due to a miscalculation in the pregnancy date.

A Word From Verywell

Monitoring hCG levels provide healthcare providers with the means to assess the health of the pregnancy and to ensure that the baby is delivered to term without complication. If hCG levels are not where they should be, this can cause considerable stress, especially if you have to wait two to three days between evaluations.

Try not to make assumptions and ask your doctors as many questions as you need to get a grasp of what the tests are actually saying. Oftentimes, we only hear the worse-case scenario and disregard everything else. While this is natural—a defense mechanism to help us "prepare for the worst"—it neither helps you nor your peace of mind.

Take things one step at a time, and turn to your friends and loved ones for support until you have the answers you need.

Source:

Slattengren, A.; Prasad, S.; and Oyola, S. "Is this pregnancy viable?" Journal of Family Practice. 2013; 62(6): 305-316.

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