What Is Subchorionic Haematoma

Introduction

Definition of subchorionic haematoma

Subchorionic haematoma is a collection of blood between the chorionic membrane and the uterine wall caused by the separation of the chorion from the endometrium during pregnancy.¹ The chorionic membrane is the outermost layer of the amniotic sac which surrounds the developing foetus and separates the amniotic sac from the uterus. The most common symptom of subchorionic haematoma is vaginal bleeding. Subchorionic haematoma is the most common cause of first-trimester bleeding. However, some subchorionic haematomas are asymptomatic and may only be discovered during a routine prenatal ultrasound.² Most subchorionic haematomas shrink in size and eventually disappear on their own.

The importance of understanding subchorionic haematoma

The prevalence of haematomas seems to vary greatly, with a reported incidence of between 0.46% to 39.5%.³  Studies have shown that subchorionic haematoma is associated with an increased risk of miscarriage, premature birth, placental abruption, premature rupture of membranes, low birth weight and foetal growth restriction. The size of the subchorionic haematoma may also be significant, as a large subchorionic haematoma before 12 weeks of gestational age was shown to have an increased risk of adverse pregnancy outcomes.⁴ Subchorionic haematomas have been reported more frequently in the infertile population or those undergoing fertility treatment. However, it is possible subchorionic haematomas are more frequently detected in those undergoing fertility treatment because these patients are more likely to be having early ultrasounds.⁵ 

Causes and risk factors

The exact cause of subchorionic haematoma is still unclear. Some studies have shown poor placentation (attachment, implantation and placental development) to be an underlying cause, as it can lead to the formation of weak blood vessels that easily tear.

The following risk factors have been associated with subchorionic haematoma:

• uterine irregularities
• pelvic infections
• a history of uterine trauma
• recurrent miscarriages
• IVF pregnancy, particularly using a frozen-thawed embryo transfer
• high blood pressure

Symptoms

As mentioned above some subchorionic haematomas don’t cause any symptoms, and are only detected during a routine pregnancy ultrasound.

For those patients that do experience symptoms, the main symptom is vaginal bleeding. Some patients may also experience abdominal or back pain or discomfort.

Diagnosis

If you are suffering from vaginal bleeding during your pregnancy you should contact your healthcare provider immediately so that a possible cause can be determined. Your healthcare provider will take your medical history and ask about any other symptoms. 

You will then be given an ultrasound to look at the possible cause of the bleeding.

Some asymptomatic subchorionic haematomas may be discovered during a routine pregnancy scan.

Differential diagnosis

Bleeding and abdominal pain during pregnancy is common and there are many other causes, therefore a proper evaluation of the patient needs to be done. Some possible other causes are:

• miscarriage
• ectopic pregnancy
• implantation bleeding
• bleeding after sex while pregnant
• an infection
• placenta conditions like placenta previa or placental abruption

Treatment and management

Many subchorionic haematomas will go away on their own over time. Your doctor will use an ultrasound to determine the location and size of the haematoma and the baby’s gestational age.

Your treatment plan will depend on these factors, your symptoms, and your health history.

Some of the following treatments for subchorionic haematomas may be used:

• complete bed rest 
• no heavy lifting
• no exercise, or a reduction in exercising
• avoiding sex
• hospitalisation
• follow-up ultrasounds to check the size of the haematoma
• monitoring of symptoms such as cramps and early labour like contractions
• anti-D immune globulin should be given to patients who are RhD negative and have vaginal bleeding
• progesterone pessaries which are inserted in the vagina may be used in some cases; although their efficacy has not been proven, they can help improve the outcome of a pregnancy³

Risks and complications

Having a subchorionic haematoma may increase your chances of pregnancy complications. You may develop some of the following complications:

• early or late pregnancy loss
• premature birth
• placental abruption
• heavy vaginal bleeding

Subchorionic haematoma diagnosed at the beginning of a pregnancy is a risk factor for pregnancy-induced hypertension in the third trimester.⁶      

Prognosis

For people assigned female at birth (AFAB) the pregnancy outcome is dependent on the AFAB’s age, the size of the haematoma, and the gestational age. A large haematoma increases the risk of miscarriage. The earlier in a pregnancy the subchorionic haematoma is identified the higher the risk of an adverse outcome.

The location of the haematoma also plays a role in the outcome. The likelihood of an adverse outcome is greater when the location of the haematoma is retroplacental versus marginal.⁶

FAQs

How common is a subchorionic haematoma?

Subchorionic haematomas are the most common cause of first-trimester bleeding. Their incidence seems to vary greatly, with a reported incidence between 0.46% and 39.5%.

Is a subchorionic haematoma high-risk pregnancy?

Whether a pregnancy is considered high risk depends on the size of the haematoma and whether you have any other health conditions. A large haematoma or one that causes excessive vaginal bleeding will likely be considered a high-risk pregnancy. A small haematoma with only minor or no bleeding will most likely not be considered a high-risk pregnancy and just require a follow-up scan.

Can a subchorionic haematoma cause a miscarriage?

Most subchorionic haematomas heal on their own and won’t cause any complications. However, there is a small risk of miscarriage. The risk is greater if the haematoma is large or it is diagnosed very early in pregnancy.

How quickly do subchorionic haematomas heal?

Most subchorionic haematomas will heal and disappear over a few weeks. Some large haematomas may not resolve on their own and cause complications.

What should I avoid with a subchorionic haematoma?

Depending on the size and severity of the haematoma, patients suffering from a subchorionic haematoma should avoid heavy lifting, exercise and sex. Some patients may also require bed rest or hospitalisation.

Summary

Subchorionic haematoma is a condition affecting some pregnant people. It is caused by the collection of blood between the uterine wall and the chorionic membrane. It often results in vaginal bleeding during the first trimester and can cause distress for expectant people. The prognosis for pregnancies with subchorionic haematomas varies depending on the size and location of the haematoma and also the medical history of the pregnant person. A subchorionic haematoma, especially a large one, can increase the risk of complications during pregnancy or lead to an adverse outcome. Patients with a large haematoma may require bed rest or a reduction in physical activity. Regular monitoring through ultrasounds are essential for monitoring the progression of the haematoma and the overall health of the pregnancy. Most cases of subchorionic haematoma will resolve on their own over time and the pregnancy will result in a successful outcome. Pregnant people experiencing symptoms such as bleeding should contact their healthcare provider to ensure appropriate management and the best possible outcome.