A subchorionic hematoma is a common finding in early pregnancy, where blood collects between the uterine wall and the developing pregnancy. This condition is frequently detected when vaginal bleeding occurs, leading to an ultrasound examination. While its presence can be concerning, many subchorionic hematomas resolve without causing significant issues for the pregnancy.
What is a Subchorionic Hematoma?
A subchorionic hematoma, also called a subchorionic hemorrhage, is a collection of blood that forms between the chorion (the outer membrane surrounding the embryo) and the uterine wall. This occurs when the chorionic membrane partially detaches from the uterine lining. The exact cause of this separation is often unclear.
The most common sign of a subchorionic hematoma is vaginal bleeding, which can vary from light spotting to heavier flows, sometimes accompanied by clots. Some individuals may also experience mild pelvic cramping or abdominal discomfort. However, many people with a subchorionic hematoma have no symptoms at all, and the condition is discovered incidentally during a routine ultrasound examination.
How Subchorionic Hematomas are Measured and What Size Means
Subchorionic hematomas are measured using ultrasound, with dimensions given in millimeters (mm). Their size is assessed in relation to the gestational sac, the fluid-filled sac enclosing the embryo. This proportional measurement helps determine the potential impact on the pregnancy. There isn’t a single “average” size, as hematomas exist on a spectrum from very small to large.
Hematomas are classified based on their size relative to the gestational sac to estimate potential risks. A hematoma is considered small if it is less than 20% of the gestational sac’s size, medium if it ranges from 20% to 50%, and large if it is greater than 50%. Smaller hematomas, particularly those detected later in the first trimester, carry a lower risk and often resolve on their own. Larger hematomas, especially if diagnosed early in pregnancy, may be associated with an increased chance of complications. These complications can include miscarriage, preterm labor, or placental abruption.
Managing a Subchorionic Hematoma
Management of a subchorionic hematoma primarily involves watchful waiting and close monitoring. There is no specific treatment to remove the blood collection; instead, the focus is on supportive care to help the hematoma resolve naturally and manage symptoms. Most subchorionic hematomas shrink and disappear on their own as pregnancy progresses.
Recommendations often include avoiding strenuous activities, refraining from lifting heavy objects, and abstaining from sexual intercourse to prevent further irritation or bleeding. Regular follow-up ultrasounds are usually scheduled to monitor the size and progression of the hematoma, ensuring it is resolving as expected. Extended bed rest is generally not recommended, as research has not shown it to improve pregnancy outcomes for subchorionic hematomas and can carry its own risks.
When to Contact Your Doctor
Contact your doctor immediately if you experience a significant increase in vaginal bleeding, especially if it is heavy enough to soak through a sanitary pad every hour for two or more hours, or if you pass large blood clots.
Other concerning symptoms that warrant prompt medical evaluation include severe or worsening abdominal pain, persistent cramping, dizziness or lightheadedness, or any signs that might indicate preterm labor. If you pass any tissue, saving it for your healthcare provider to examine can also be helpful.