Bleeding during pregnancy is certainly a cause for worry. After all, pregnancy (in theory) should not cause vaginal bleeding. Still, there are other causes of bleeding besides menstruation. Vaginal bleeding in some form occurs in about half of all pregnancies.

In pregnancy, some types of bleeding are a big issue, while others are not. Subchorionic bleeding is just one type of bleeding. Some cases can become serious, while others don’t adversely affect the pregnancy. But it’s important to call your doctor right away when you experience any form of vaginal bleeding.

Subchorionic Bleeding, Explained

Subchorionic bleeding occurs when the placenta detaches from the original site of implantation. This is called a subchorionic hemorrhage or hematoma. It affects the chorionic membranes. These membranes lift apart and form another sac between the placenta and the uterus. The movement and resulting clots are what cause this type of bleeding.

These hematomas can range in size, with the smallest being most common. Larger versions can cause heavier bleeding.

How It’s Different from Other Types of Bleeding

Subchorionic hematomas are just one cause of bleeding in pregnancy. Their precise cause is not known. They’re also not the same as “spotting.”

Spotting occurs in about 20 percent of women within 12 weeks of their pregnancies, according to the American Pregnancy Association. While spotting can occur at any stage of pregnancy, it’s most common in the first trimester.

Causes of spotting include:

  • implantation
  • uterine expansion
  • intercourse
  • hormone level increases
  • cervical changes, including cervical polyps (small growths)
  • vaginal exams

Spotting is exactly as it sounds — a few spots of blood. While it’s still a good idea to report any form of spotting to your doctor, the symptoms are very different from vaginal bleeding.

Bleeding that goes beyond a few spots and requires a panty liner is often a sign of something else. Subchorionic bleeding is one such possibility. Bleeding tends to be the only sign or symptom of subchorionic hematoma. You may not even realize you have one until your doctor performs an ultrasound.

Heavy bleeding can also be a sign of:

  • ectopic pregnancy (egg fertilizes outside of the womb)
  • miscarriage
  • molar pregnancy (a rare condition that results in a mass of tissue in the womb)
  • uterine rupture
  • separation of the placenta from the uterus
  • preterm labor (earlier than 37 weeks)

These more serious causes of vaginal bleeding are also accompanied by other symptoms, like severe abdominal pain and dizziness.

Is Subchorionic Bleeding Harmful?

Many subchorionic hematomas aren’t harmful in the long term. Your doctor will have a better idea after looking at the hematoma on an ultrasound. Smaller hematomas have better outcomes, while larger versions can present problems. According to a study published in the American Journal of Roentgenology, approximately 7 percent of hematomas result in miscarriage. The earlier you seek a diagnosis, the better the outcome.

Prompt Treatments Are Key

If a diagnosis of vaginal bleeding is deemed subchorionic, then your doctor will likely start treatments to prevent miscarriage. Options may include progesterone or dydrogesterone. If the hematomas are large, you may also be ordered to:

  • stay in bed (bed rest)
  • avoid standing for long periods of time
  • avoid sex
  • avoid exercise

Follow Up with Your Doctor

Subchorionic bleeding is a sign of a related hematoma. While not considered a normal occurrence in pregnancy, these hematomas aren’t unusual. They also don’t necessarily mean the pregnancy will fail. With treatment and close monitoring, many women go on to deliver healthy babies at full term.

Even though subchorionic bleeding doesn’t pose an immediate threat like other types of vaginal bleeding, you should still follow up with your doctor. Call your doctor whenever you experience any bleeding or spotting. If the cause is unknown, an ultrasound may be performed to rule out hematoma.