What Is a Subchorionic Hemorrhage in Pregnancy?

At 12 weeks pregnant, when many people are preparing to share their big news, I was keeping mine a closely guarded secret. Each time I went to the bathroom, the familiar pangs of anxiety returned as I wondered time and time again, was this bleed different? Was this the bleed that meant I was losing my baby? 

Each time my baby was fine. I wasn't miscarrying; I was experiencing symptoms of a subchorionic hematoma, also referred to as subchorionic hemorrhage and subchorionic bleeding.

Subchorionic hematomas are an anomaly usually associated with persistent bleeding that starts in the first trimester. In my (rather extreme) case, it meant that I bled from weeks 6 to 27—sometimes with medium-sized clots the size of my palm—and I was in and out of hospital for much of my pregnancy.

But despite the dramatic presentation, experts say subchorionic hematomas are relatively common and often don't cause serious issues in pregnancy.

What Causes a Subchorionic Hematoma?

A subchorionic hematoma or subchorionic hemorrhage occurs when blood collects between the wall of the uterus and the membrane sac that surrounds the fetus. 

"This typically results from a partial detachment of the membrane, known as the chorion, from the wall of the uterus," explains Robin Kalish, M.D., FACOG, a maternal-fetal medicine specialist and director of clinical maternal-fetal medicine at NewYork-Presbyterian/Weill Cornell Medicine in New York City. 

While the exact cause of the separation is usually unknown, there is an upside: "Most pregnancies with a subchorionic hematoma will have normal outcomes," adds Dr. Kalish.

Risk Factors for a Subchorionic Hematoma

While it's often unclear what causes a subchorionic hematoma, certain modifiable risk factors could contribute to a hematoma growing, says Mackenzie Naert, M.D., a clinical fellow in obstetrics and gynecology at Brigham and Women's and Massachusetts General Hospital in Boston.

One of those factors is being on blood thinners. "In certain cases, a patient and physician may decide to hold the blood thinners for a patient with a hematoma,” says Dr. Naert. 

Here are some other factors that can put a patient at risk for a subchorionic hematoma:

• Uterine malformation
• History of recurrent pregnancy loss
• Pelvic infections
• IVF pregnancies

Still, many patients with a subchorionic hematoma will have no risk factors, and they'll never know the cause. I didn't discover what caused my subchorionic hematoma, and by the time it eventually resolved, it was rarely discussed again.

“Overall, it isn't necessary or possible to identify a cause of the hematoma since there is not much to do other than monitor for any bleeding,” explains Dr. Naert. 

How Common Is a Subchorionic Hematoma?

Vaginal bleeding can happen in all stages of pregnancy and affects up to 25% of pregnant people in the first trimester. Subchorionic hematomas are the most common cause of bleeding from 10 to 20 weeks, contributing to about 11% of all cases.

"Subchorionic hematomas are quite common and are probably more widely experienced than people expect," says Dr. Kalish.

Subchorionic Hematoma Pregnancy Symptoms

Bleeding is a common symptom of subchorionic hematoma and can range from light spotting to heavy. Bleeding was the first symptom I had at around 6 weeks. It intensified at week 12 and continued until week 27. 

While some pregnant people will experience spontaneous bleeding like me, others may also experience cramps or have no symptoms at all.

How Is a Subchorionic Hematoma Diagnosed?

The first step in diagnosing a subchorionic hematoma is usually an ultrasound, which can indicate the size and location of the bleed. All bleeding should be investigated to rule out miscarriage, ectopic pregnancy, or an infection.

How Serious Is a Subchorionic Hemorrhage?

The data is mixed, but generally speaking, subchorionic hematomas shouldn't cause too much concern. Even where risks may be associated, many pregnant people will go on to deliver healthy babies regardless of their symptoms.

With that said, one study found a subchorionic hematoma could carry an increased risk of adverse outcomes, including early pregnancy loss, fetal growth restriction, placental abruption, or preterm delivery. But other research hasn’t found a clear correlation between subchorionic hematomas and negative outcomes.

Experts say size could play a role in the impact of subchorionic hematomas. Dr. Kalish considers a small subchorionic hematoma as a bleed that encompasses less than 20% of the pregnancy sac, while a larger one could involve more than 50%. "While larger subchorionic hematoma are associated with a higher risk of adverse pregnancy outcomes, ongoing bleeding–especially when heavy and associated with cramping or pain–is more worrisome than the subchorionic hematoma size alone," she says.

Can a Subchorionic Hemorrhage Cause a Miscarriage?

While some research has found a connection between subchorionic hematoma and miscarriage, the evidence isn’t clear. 

In her 2019 research of the correlation, Dr. Naert found reassuring results. "Historically, people have thought that subchorionic hematomas were associated with a higher risk of miscarriage but our study did not find this," she explains. "Certainly there is still a lot we may not know about hematomas, but with the current data, I feel confident reassuring patients that the subchorionic hematoma itself does not increase the risk of miscarriage."

Treating a Subchorionic Hematoma

Once a subchorionic hematoma is diagnosed, there's typically not much that can be done besides ongoing monitoring and follow-up appointments with your health care provider. Most subchorionic hematomas will resolve on their own, like mine eventually did—and today I have a beautiful, healthy (and very cheeky!) child.

There's various information available around home remedies like bed rest, and even drinking pomegranate juice. However, generally speaking, none of these are backed by science. "There is nothing anyone can do with subchorionic hematomas to help it go away or improve," explains Dr. Naert.

A provider may suggest avoiding sexual intercourse. “But not because the subchorionic hematoma is caused or worsened by intercourse,” says Dr. Naert. “Intercourse during pregnancy can cause bleeding from the cervix even in the absence of a hematoma and this bleeding can blur the picture.” 

As for bed rest, she says that can actually increase the risk of blood clots. And heavy lifting should be avoided throughout all trimesters, both for patients with and without subchorionic hematomas. 

The best thing you can do is stay connected with your health care provider who will continue to monitor you and your fetus throughout your pregnancy.

The Bottom Line

Subchorionic hematomas can cause light to heavy bleeding during pregnancy. While most pregnancies will have normal outcomes, vaginal bleeding is always a reason to connect with your medical provider.

It’s important for pregnant people to know they did nothing wrong. "For patients with bleeding early in pregnancy, I reassure them that there was nothing they did to cause the bleeding, and similarly nothing they can do to stop it,” explains Dr. Naert. “It just takes time to know the significance of the bleeding and, in the majority of cases, the pregnancy will be fine."