GUIDE
A subchorionic hematoma (SCH) is a collection of blood between the placenta (or chorion) and the uterine wall. It is one of the most common causes of first-trimester bleeding.
Subchorionic hematomas are found in about 1 to 3 percent of all pregnancies and up to 20 percent of pregnancies with first-trimester bleeding. Most are small, cause no problems, and resolve on their own. Understanding what they are can ease the anxiety that comes with unexpected pregnancy bleeding.
Be prepared from day one
A subchorionic hematoma forms when blood collects between the chorionic membrane (the outer layer surrounding the embryo and the developing placenta) and the wall of the uterus. Think of it as a bruise — blood has leaked from the developing placental tissue and pooled in a small space.
The exact cause is not always known, but it is believed to occur during implantation when the placenta is embedding into the uterine lining. Some bleeding at the edge of the developing placenta is common and usually harmless.
Subchorionic hematomas are found in 1 to 3 percent of all pregnancies, but they are much more common in pregnancies that experience first-trimester bleeding — found in up to 20 percent of those cases. If you are experiencing bleeding during pregnancy, a subchorionic hematoma is one of the first things your provider will look for on ultrasound.
The color and amount of bleeding from a subchorionic hematoma can vary widely. Brown blood is older and often less concerning than bright red. Both are common with hematomas.
Subchorionic hematomas are diagnosed by ultrasound. They appear as a dark (anechoic or hypoechoic) area between the gestational sac and the uterine wall. Your provider will note the size, location, and relationship to the placenta.
Size matters for prognosis. Small hematomas — those less than about 20 percent of the gestational sac size — rarely cause problems. Medium hematomas (20 to 50 percent) are watched more closely. Large hematomas (greater than 50 percent of the sac) carry a higher risk of complications, including miscarriage and preterm birth, though many still resolve.
Follow-up ultrasounds every 2 to 4 weeks track whether the hematoma is shrinking, stable, or growing. A shrinking hematoma is a positive sign. The location also matters — hematomas near the edge of the placenta or behind the area where the placenta attaches may be watched more carefully.
Most subchorionic hematomas are benign findings, but certain characteristics warrant closer monitoring. Large hematomas, those diagnosed before 9 weeks, hematomas that grow on serial ultrasounds, and those accompanied by heavy bleeding are associated with slightly higher risks.
The potential complications include miscarriage (primarily in the first trimester), preterm birth, placental abruption (the placenta separating from the uterine wall), and premature rupture of membranes. However, it is important to emphasize that even in higher-risk cases, many pregnancies continue normally.
If your subchorionic hematoma is large or not resolving, your provider may classify your pregnancy as high-risk and increase monitoring. This additional attention is a precaution, not a prediction.
The most reassuring fact about subchorionic hematomas is that the majority resolve without affecting the pregnancy. Small hematomas (less than 20 percent of the gestational sac) have an excellent prognosis. Even moderate-sized hematomas usually shrink over time as the body reabsorbs the blood or it drains through the vagina.
If you are bleeding, keep a record of the timing, amount, color, and any associated symptoms. Use pads (never tampons) so you can accurately assess the volume. This information is valuable for your provider at follow-up appointments and helps them determine whether the hematoma is resolving or worsening.
Your provider will likely schedule follow-up ultrasounds every 2 to 4 weeks to monitor the size of the hematoma. Seeing it shrink is reassuring. If it stays the same or grows, your provider will adjust your care plan. Keep these appointments — they are the best way to monitor the situation.
Bleeding during pregnancy is frightening, even when you have been told the hematoma is likely harmless. The uncertainty can be stressful. Talk to your provider about your concerns, lean on your support system, and consider our guide on pregnancy after miscarriage if previous loss is adding to your anxiety. Take it one ultrasound at a time.
Any change in bleeding or new symptoms should be reported. Your provider would rather hear from you than have you worry in silence.
Heavy bleeding or severe pain during pregnancy always warrants emergency evaluation, regardless of a known hematoma.
The vast majority of subchorionic hematomas resolve on their own and do not affect the outcome of the pregnancy. Even those that cause alarming bleeding episodes often shrink and disappear as the pregnancy progresses.
Once the hematoma resolves — confirmed on ultrasound — any activity restrictions can usually be lifted. Most people with a resolved subchorionic hematoma go on to have completely normal pregnancies and deliveries.
For related information, see our guides on bleeding during pregnancy, miscarriage signs and support, placenta previa, high-risk pregnancy, and pregnancy after miscarriage.
This guide is for informational purposes only and is not a substitute for professional medical advice. Always consult your healthcare provider with any questions about your pregnancy.
