Researchers have found an association between low levels of the hormone human chorionic gonadotropin (hCG) and pregnancy loss or miscarriage.

Sex and gender exist on spectrums. This article will use the terms “male” and “female” to refer to a person’s sex assigned at birth.”

As high as 26% of all pregnancies end in pregnancy loss. There are multiple potential causes, such as chromosomal abnormalities.

However, it is important to note that while this figure appears high, it also includes unknown pregnancies, not just confirmations from positive pregnancy test results. Sometimes, people experience miscarriages without knowing they were pregnant.

The medical community has tried to investigate other detectable and potentially treatable causes. With this in mind, researchers are looking into hCG levels and how they relate to pregnancy loss.

This article explores the research-based connections between low hCG levels and pregnancy loss.

Doctors often call hCG “the pregnancy hormone” because cells in a pregnant female’s placenta produce the hormone to help the fertilized egg grow.

A person’s hCG levels start to increase about 48 hours after the fertilized egg implants in the uterus.

Typically, hCG levels will double every 48 hours until anywhere from 8–11 weeks, when they will start to taper off.

Sometimes, doctors will use hCG levels to correlate the likelihood of pregnancy development and loss in the first trimester.

Researchers have identified links between hCG levels and the expected development of a fetus that a healthcare professional can observe via ultrasound.

Levels of hCG in the blood correlate with the following fetal development markers:

  • 800–1,500 international units per liter (UI/L) of hCG: small visible gestational sac
  • 4,500–7,500 IU/L of hCG: visible yolk sac
  • 8,650–12,200 IU/L of hCG: visible fetal heart motion

If a doctor views a fetus using an ultrasound but does not see the expected growth, they may order an hCG blood test. If hCG levels are much lower than expected, they may predict that the fetus may not be viable.

It is important to note that hCG levels do not necessarily cause pregnancy loss. Instead, doctors take these levels into account with other factors as part of a trend. After analyzing the trend, healthcare professionals can get an idea of how the pregnancy is progressing.

When an ectopic or intrauterine pregnancy develops, it presents with low or insufficiently increasing hCG levels. Low hCG levels are not a cause but a symptom of these conditions.

Doctors look at two factors when considering hCG levels and pregnancy — what the initial hCG level was and how fast it increases over the pregnancy.

Therefore, low hCG levels can be relative, and doctors are more concerned with how they increase over time.

Levels of hCG typically double every 48 hours in an estimated 99% of viable pregnancies within the first several weeks of pregnancy.

Currently, there is no evidence to suggest that administering artificial hCG hormones to boost a pregnant person’s levels can prevent pregnancy loss. With this in mind, low hCG levels are a symptom of pregnancy loss, not a cause.

Measuring hCG levels helped predict pregnancy viability

A 2018 study found that repeatedly measuring hCG levels helped predict the early viability of pregnancies in 41.1% of participants.

The researchers found that taking hCG measurements over 48 hours could predict pregnancy viability more quickly than taking transvaginal ultrasounds about 1–2 weeks apart.

While knowing hCG levels may be helpful, it is not an absolute indicator that a person will experience pregnancy loss.

The risk of pregnancy loss is greatest in the first trimester, which coincides with rising hCG levels.

Doctors may measure an individual’s hCG levels if they suspect the pregnancy may not be progressing as expected.

Healthcare professionals are usually less concerned with the initial hCG measurement. Instead, they are more interested in whether a female’s hCG levels rise at the expected rate.

With this in mind, low hCG levels do not trigger pregnancy loss — it may be due to other causes.

Additionally, administering artificial hCG has not been shown to reduce the risk of pregnancy loss.

A person who experiences recurring pregnancy loss should speak to their doctor about potential tests and treatments for fertility.