Subchorionic Hematoma and Pregnancy Risks

Condition Characterized by Partial Placental Detachment

Subchrionic Hematoma symptoms

Verywell / Gary Ferster 

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Bleeding during pregnancy can be alarming but isn't always a sign of an impending miscarriage. Sometimes bleeding is a symptom of a fairly common type of blood clot called a subchorionic hematoma (also known as subchorionic hemorrhage). 

According to experts at University of Michigan Health, this type of hematoma is caused by "bleeding under one of the membranes (chorion) that surrounds the embryo." Why this happens isn't entirely understood, but there are several possible causes.

Although there's nothing that can be done about a subchorionic hematoma, in some cases treatments wouldn't be necessary even if they existed. Many people who develop subchorionic hematomas enjoy otherwise normal pregnancies. While some studies have shown that this condition increases the risk of pregnancy loss, the research is inconclusive.

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Causes

The causes of subchorionic hematoma aren't fully understood. However, research suggests that maternal conditions such as blood clotting disorders, preeclampsia, and trauma, as well as maternal use of drugs that cause blood vessels to dilate (such as cocaine and methamphetamines) could play a role.

Risk Factors

There are some suspected risk factors for subchorionic hematomas. Studies have found they're more likely to occur in pregnancies that are conceived via in vitro fertilization (IVF) or frozen-thawed embryo transfer, for example.

While bleeding from a subchorionic hematoma can be alarming, it is rarely a sign of a miscarriage. If the hematoma develops early in pregnancy, the chances of carrying your baby to term are good.

Symptoms

Bleeding caused by a subchorionic hematoma can range from a heavy flow with clots to light spotting to no bleeding at all, in which case the only reason the clot is discovered is that it shows up during an ultrasound.

Vaginal bleeding is estimated to affect as many as one in four people during the first half of pregnancy and is a common reason for first-trimester ultrasonography. Some women also have some cramping, especially if the bleeding is significant.

Complications

Hematomas found during the early part of the first trimester tend to be less problematic than those discovered later in the first or second trimester. And generally speaking, small hematomas on the surface of the placenta are far less concerning than those that develop under the placenta or behind the fetal membrane.

Hematomas that don't grow also are less worrisome, but those that do may cause the placenta to pull away from its attachment site on the uterus. If more than 30% of the placenta becomes dislodged, it could cause the hematoma to grow even larger. This may set off a domino effect in which the membranes (amniotic sac) ruptures prematurely, leading to spontaneous abortion.

In fact, research has found that subchorionic hematoma can increase the risk of an array of pregnancy complications, including miscarriagepreterm laborplacental abruption, and premature rupture of membranes.

The risk of complications is largely related to the size of the subchorionic hematoma, how far along the pregnancy is, and the parent's age.

Treatment

Once a subchorionic hematoma forms there's nothing a doctor can do about it. There's no treatment for these blood clots. However, they can be managed. If you develop one, depending on the location and size of the hematoma, your doctor may advise you to come in for regular follow-up exams.

You would also be advised to avoid strenuous activity, heavy lifting, or excessive exercise. You may need frequent rest to prevent increases in blood pressure, and your doctor may also advise against travel.

In rare cases, a doctor may recommend blood thinners to bleed the clot out. If the chances of miscarriage are high, some doctors will use estrogen and progesterone to slow or prevent further hemorrhaging.

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7 Sources
Verywell Family uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. University of Michigan Health. Subchorionic hemorrhage. Updated October 8, 2020.

  2. San Diego Perinatal Center. Subchorionic hematoma.

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  4. Asato K, Mekaru K, Heshiki C, et al. Subchorionic hematoma occurs more frequently in in vitro fertilization pregnancy. Eur J Obstet Gynecol Reprod Biol. Oct 2014;181:41-4. doi:10.1016/j.ejogrb.2014.07.014

  5. Amirkhani Z, Akhlaghdoust M, Abedian M, et al. Maternal and perinatal outcomes in pregnant women with first trimester vaginal bleeding. J Family Reprod Health. 2013;7(2):57-61.

  6. Tuuli MG, Norman SM, Odibo AO, Macones GA, Cahill AG. Perinatal outcomes in women with subchorionic hematoma: a systematic review and meta-analysis. Obstet Gynecol. 2011;117(5):1205-1212. doi: 10.1097/AOG.0b013e31821568de

  7. Coomarasamy A, Devall AJ, Cheed V, et al. A randomized trial of progesterone in women with bleeding in early pregnancy. New England Journal of Medicine. 2019;380(19):1815-1824. doi:10.1056/NEJMoa1813730