A subchorionic bleed is also called a subchorionic hemorrhage. It refers to a collection of blood that develops between the gestational membranes, such as the placenta, and the uterus during pregnancy.

This accumulation of blood can lead to vaginal bleeding during pregnancy. This article will look at the causes and risks of a subchorionic hemorrhage (SCH) and explore other reasons for vaginal bleeding during pregnancy.

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Subchorionic bleeding is when blood collects between the uterus and the gestational membranes during pregnancy.

Vaginal bleeding during pregnancy is common, with 16–25% of pregnant people experiencing some vaginal bleeding during the first trimester of pregnancy. SCH accounts for around 11% of vaginal bleeding cases in 10–20 weeks of gestation.

Many people experience light bleeding or spotting from the vagina during pregnancy. That said, this spotting does not require a pad or tampon, and it can occur between conception and giving birth.

Some other causes of bleeding or spotting in early pregnancy are:

While bleeding during pregnancy is common, it may indicate a dangerous complication in the pregnancy.

Other more serious causes of bleeding in early pregnancy include:

  • pregnancy loss
  • ectopic pregnancy, when a fertilized egg implants somewhere other than the uterine cavity
  • molar pregnancy, a rare mass of tissues that forms inside the womb instead of a fetus

It is unclear why SCH occurs in some people and not others. It may result from a partial separation between the chorionic membrane from the walls of the uterus.

The collection of blood between the womb and the gestational membranes can result in blood clots called subchorionic hematomas, which can be small or large and may lead to vaginal bleeding.

The main symptom of SCH is vaginal bleeding, but a pregnant person may also feel discomfort and tenderness and a pain in the belly or back that comes on suddenly and does not go away.

Some people will not experience any symptoms and will only find out they have SCH during a routine ultrasound examination.

Subchorionic bleeding does not usually cause any problems. However, scientific research is inconclusive on whether SCH can cause pregnancy complications, such as preterm delivery or pregnancy loss.

For example, a 2014 study found that vaginal hemorrhage accompanying a subchorionic hematoma increased the risk of miscarriage before 20 weeks in people with threatened abortion.

However, a further study found that SCH did not increase the risk of pregnancy loss before 20 weeks.

Another possible complication is placental abruption, a severe complication when the placenta detaches from the womb lining.

Anyone who experiences vaginal bleeding during pregnancy should contact a doctor.

To diagnose the cause of the bleed, a healthcare professional will usually perform a physical examination and order blood tests and an ultrasound examination.

An ultrasound uses high-frequency sound waves to generate a black and white image of the fetus and placenta on a screen. If a person is experiencing subchorionic bleeding, the areas of blood inside the uterus may show up on this picture.

These tests will assist doctors in ruling out any associated conditions that may be causing vaginal bleeding.

The treatment for SCH will depend on a person’s symptoms, age, and overall health status.

For example, an individual with a stable pregnancy and no significant blood loss may be able to recover from SCH with close surveillance and supportive care. However, the condition represents a serious medical emergency if a person has a bleeding disorder.

Therefore, a doctor may wish to monitor people with SCH in the hospital until the bleeding stops or the SCH itself resolves.

Although subchorionic bleeding is common in the first trimester, it is still best to speak with a doctor to get a correct diagnosis whenever bleeding occurs in pregnancy.

Most SCHs are not harmful, but some research suggests they may have associations with certain adverse pregnancy complications.