A subgaleal hematoma (SGH) is a form of birth trauma involving bleeding into a specific area of a newborn’s scalp, typically linked to mechanical stresses during the process of delivery. The resulting massive, spreading scalp swelling requires immediate and close monitoring. While most cases resolve completely with proper medical care, the potential for significant blood loss means early recognition and intervention are crucial for a positive outcome.
Location and Definition
A subgaleal hematoma is defined by the accumulation of blood in the loose areolar tissue, a potential space located just beneath the galea aponeurotica and above the skull’s periosteum. The bleeding occurs in this area, known as the subgaleal space. The hematoma forms when emissary veins, which connect the veins of the scalp to the deeper veins within the skull, are ruptured due to a shearing force.
This space is not confined by the skull’s suture lines, unlike a cephalohematoma which is trapped beneath the periosteum. This allows the blood collection to spread widely across the entire cranial vault. Because the space can hold up to 20% to 40% of a newborn’s total blood volume, the condition carries a risk of life-threatening hemorrhagic shock.
Primary Causes and Risk Factors
The formation of a subgaleal hematoma is directly related to the mechanical forces exerted on the baby’s head during labor and delivery. The primary mechanism involves a shearing force that separates the scalp from the skull, tearing the small blood vessels. This separation is most commonly associated with instrumental delivery, where external traction or pressure is applied.
The single greatest risk factor for SGH is vacuum-assisted delivery (ventouse delivery), accounting for up to 90% of neonatal cases. The vacuum’s suction applies negative pressure, causing delicate layers to separate and emissary veins to rupture. Forceps delivery is another risk factor. Other factors that increase the likelihood of injury include prolonged labor, a large fetal head size (macrosomia), or a neonatal clotting disorder.
Recognizing the Clinical Signs
The clinical presentation of a subgaleal hematoma is a distinctive swelling that typically develops gradually over the first 12 to 72 hours following birth. The swelling appears as a soft, diffuse, and fluctuant mass that can shift with movement. A defining feature is its ability to cross the cranial suture lines, which differentiates it from a cephalohematoma confined to the surface of a single skull bone.
The most concerning clinical signs indicate significant blood loss and hypovolemia. Clinicians may notice a visible increase in the infant’s head circumference, accompanied by pallor, an abnormally fast heart rate (tachycardia), and lethargy. Diagnosis is generally made through a physical examination. Imaging tools like an ultrasound or CT scan are often used to confirm the diagnosis, measure the size, and rule out associated skull fractures or intracranial bleeding. Laboratory tests monitor the baby’s blood count to quantify the extent of blood loss and anemia.
Management and Expected Recovery
Management of a subgaleal hematoma focuses primarily on supportive care and close monitoring. Newborns diagnosed with SGH require admission to a neonatal unit for continuous observation of vital signs, head circumference, and blood count. This monitoring ensures that ongoing blood loss is promptly identified and addressed.
If blood loss causes anemia or hemorrhagic shock, the infant may require medical intervention, such as intravenous fluids or a blood transfusion. Aspiration or draining of the hematoma is generally avoided due to the high risk of introducing infection. Most subgaleal hematomas resolve spontaneously over several weeks to months as the body reabsorbs the pooled blood. With early detection and appropriate management, the long-term prognosis is usually excellent.