A subchorionic hemorrhage is a collection of blood between the uterine wall and the chorion, the outer membrane that surrounds the embryo during early pregnancy. It’s one of the most common causes of first-trimester bleeding, showing up on ultrasound in roughly 2 to 13% of pregnancies. Most are small, resolve on their own, and result in healthy pregnancies, but size matters: larger ones carry a higher risk of miscarriage.
Where the Bleeding Comes From
During early pregnancy, the fertilized egg implants into the uterine lining, and a membrane called the chorion develops around it. This membrane eventually becomes part of the placenta. A subchorionic hemorrhage happens when blood pools in the space where the chorion partially separates from the uterine wall. The result is a blood clot, sometimes called a subchorionic hematoma, that sits between the membrane and the uterus.
In most cases, the clot is small and the body reabsorbs it over several weeks. Large hematomas are a different story. When the separation strips 30 to 40% or more of the developing placenta away from the uterine wall, the clot can grow, compress the gestational sac, and in some cases lead to pregnancy loss.
What It Feels Like
The most recognizable symptom is vaginal bleeding, which can range from light spotting to heavier, period-like flow. Some women also experience cramping or pelvic pressure. The bleeding may be bright red if it’s fresh, or dark brown if the blood has been sitting in the uterus for a while before passing. Brown discharge is typically a sign the hematoma is draining, which is actually a good thing.
Plenty of subchorionic hemorrhages cause no symptoms at all. These are often discovered incidentally during a routine first-trimester ultrasound, which can be alarming even though “silent” hematomas tend to carry a better prognosis than those with active bleeding.
How It’s Diagnosed
Ultrasound is the primary tool. On the screen, a subchorionic hemorrhage appears as a dark, crescent-shaped area next to the gestational sac. Radiologists evaluate the size of the hematoma relative to the sac, where it sits in relation to the placenta, and how its appearance changes on follow-up scans. The hematomas typically extend to the margin of the placenta. A fresh bleed looks different from an older one because blood changes in density as it clots, so the ultrasound appearance can also help estimate how recently the bleeding occurred.
Who Is More Likely to Develop One
IVF pregnancies carry a notably higher risk. In one study, subchorionic hematomas occurred in 22.4% of IVF pregnancies compared to 11% of naturally conceived pregnancies. Within the IVF population, frozen embryo transfers and blastocyst transfers were each associated with roughly three to six times the odds of developing one.
Low-dose aspirin, which is commonly prescribed during fertility treatment and some high-risk pregnancies, has also been linked to a higher rate of subchorionic hemorrhage. One analysis found nearly a four-fold increase in patients taking aspirin compared to those who weren’t, regardless of the type of fertility treatment involved. Having had a previous pregnancy also appears to be a contributing factor.
How Size Affects Pregnancy Risk
Small hematomas, the kind that cover a minor fraction of the gestational sac, generally resolve without complications. The pregnancy continues normally, and many women never even know the hematoma was there unless it was caught on ultrasound.
Larger hematomas raise the stakes. A meta-analysis looking at first-trimester subchorionic hematomas found that in natural pregnancies, the odds of miscarriage were about three times higher than in pregnancies without one. For IVF pregnancies, the odds were about 1.5 times higher. Interestingly, the same analysis found no significant association between a first-trimester hematoma and preterm delivery, suggesting that the critical risk window is early in pregnancy rather than later.
The threshold that matters most is how much of the placenta has separated. Once 30 to 40% of the placenta detaches from the uterine wall, the risk of the hematoma growing and compressing the sac increases substantially. Below that threshold, the body can usually heal the separation and the placenta reattaches.
What Happens After Diagnosis
There is no medication that stops or shrinks a subchorionic hemorrhage. Management focuses on monitoring and reducing physical strain while the body reabsorbs the clot. Before 20 weeks, the typical recommendation is reduced activity and avoiding travel. You’ll likely be told to head to the hospital if you experience heavier vaginal bleeding, cramping, or contractions.
If you’re Rh-negative (a blood type distinction your provider will know about), you may receive an injection to prevent your immune system from reacting to the baby’s blood cells. This is a precaution taken whenever there’s bleeding during pregnancy, not something specific to subchorionic hemorrhage.
As the pregnancy progresses past 20 to 22 weeks, the approach shifts. If contractions develop, treatment for preterm labor may be started. Bleeding episodes after 24 weeks often lead to hospitalization for closer monitoring. Follow-up ultrasounds track whether the hematoma is shrinking, stable, or growing, and that trajectory guides decisions about activity level and care.
What Recovery Looks Like
Most subchorionic hemorrhages resolve by the end of the first trimester or early in the second trimester. You may continue to see brown spotting for days or weeks as the old blood works its way out, which is normal. The hematoma gradually shrinks on ultrasound until it’s no longer visible.
During this time, many providers recommend pelvic rest, meaning no sexual intercourse, and limiting strenuous exercise. The evidence behind strict bed rest for this condition is limited, and prolonged immobility carries its own risks, so most recommendations lean toward “take it easy” rather than “don’t move.” Your activity restrictions will depend on the size and location of the hematoma and whether you’re still actively bleeding.