Implications of Low hCG Levels in Early Pregnancy

During pregnancy, cells in the placenta produce a hormone called human chorionic gonadotropin (hCG). This hormone nourishes the egg after it has been fertilized and formed the embryo that attaches to the wall of the uterus. In the first trimester of a normal pregnancy, levels of hCG increase significantly, typically doubling every two to three days over the course of the first eight to 11 weeks of gestation.

When this doesn't happen—or hCG levels actually decrease—it may mean a miscarriage is taking place. Learn more about low hCG levels in early pregnancy.

How hCG Is Measured

Following conception, hCG can be detected in the blood as early as day 11 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 levels are within the normal range expected at that point in pregnancy.

In order to see how quickly hCG is doubling, serial hCG measurements are done. 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 person to person and from one pregnancy to the next. Beyond the actual number, what doctors will really want to watch is how 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:

At four weeks gestation and before, hCG levels are relatively low, but still increasing. It is generally between weeks five and six that the first significant spike in hCG production happens. By six to seven weeks, levels continue to double every three to four days, eventually reaching a peak sometime between weeks eight and 11.

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

When hCG Trends Are Abnormal

Most miscarriages occur during the first 13 weeks of pregnancy. It is at this stage that hCG monitoring is most valuable for assessing the health and status of a pregnancy. If your hCG levels are lower than they should be or are increasing more slowly than they should, or even beginning to drop, your doctor will want to figure out why. Here are possible reasons for each of these scenarios:

• A low hCG level can mean your pregnancy date was miscalculated and you're 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, or an ectopic pregnancy.
  
• 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 people experiencing symptoms of miscarriage such as heavy vaginal bleeding. Decreasing levels of hCG in the second and third trimester usually aren't a concern.
• Slow-rising hCG levels may be a sign of trouble in early pregnancy. Keep in mind, however, this occurs in around 15% of pregnancies that continue without complications.

It is also important to note that excessively high levels of hCG may indicate multiple pregnancies or a molar pregnancy, which results 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 is a useful tool for making sure a pregnancy is proceeding in a normal and healthy way, but try not to worry if your hormone levels aren't behaving as expected and your doctor is watching them closely. Ask as many questions as you need to ease your mind and stay positive. Chances are that all is well. However, if you are having a miscarriage, seek the help you need to cope and give yourself grace as you recover physically and emotionally.