A subgaleal hemorrhage (SGH) is a rare but potentially life-threatening condition in newborns involving bleeding beneath the scalp but outside the skull. This injury occurs when blood accumulates in the scalp tissue, creating a rapidly expanding mass. Because SGH can result in massive blood loss, it is considered a medical emergency requiring immediate recognition and intervention. The condition is most often associated with mechanical stress during delivery, and its severity necessitates medical awareness.
Understanding the Subgaleal Space and Hemorrhage
The scalp is composed of several distinct layers. The subgaleal space is a potential area situated within the loose areolar tissue, lying directly beneath the galea aponeurosis and above the pericranium, which is the membrane covering the skull bone. Bleeding in this space is classified as a subgaleal hemorrhage, an extracranial accumulation of blood.
The danger of SGH stems from the unique anatomy of the loose areolar layer. Unlike a cephalohematoma, which is restricted by the skull sutures, the subgaleal space is vast and unconstrained, extending over the entire top of the head. This allows for a massive and uncontrolled accumulation of blood. In a term newborn, this space can hold up to 260 milliliters of blood, potentially representing up to 80% of the infant’s total circulating blood volume.
The hemorrhage begins when the emissary veins rupture; these vessels connect the scalp veins to the dural sinuses inside the skull. When excessive shearing force is applied to the scalp, these delicate veins tear, allowing blood to rapidly pour into the unconfined subgaleal space. This rapid blood loss quickly leads to severe hypovolemic shock, where the body loses too much circulating volume to keep the organs functioning.
Primary Causes and Associated Risk Factors
The main cause of SGH is mechanical trauma or severe force applied to the newborn’s head during birth. This force disrupts the emissary veins, which are stretched and torn as the scalp is pulled away from the underlying skull. This traumatic event most frequently occurs during a difficult vaginal delivery requiring assistance from medical instruments.
Vacuum extraction is the most commonly cited cause, significantly increasing the risk of SGH compared to unassisted deliveries. The negative pressure created by the vacuum cup pulls the scalp away from the skull, leading to the shearing of the emissary veins. Forceps delivery is another form of assisted delivery that can cause the necessary mechanical stress, though it is a less frequent cause than vacuum extraction.
Several factors related to the fetus or the labor process can increase the likelihood of this trauma. Fetal macrosomia (large baby size) and a difficult or prolonged labor increase the strain on the baby’s head. A mismatch between the size of the baby’s head and the mother’s pelvis, known as cephalopelvic disproportion, can also be a contributing factor.
In rare instances, SGH can occur without the use of instruments or obvious birth trauma, suggesting an underlying issue. These non-traumatic cases often involve congenital bleeding disorders, such as hemophilia or neonatal alloimmune thrombocytopenia, which impair the infant’s ability to clot blood effectively.
Recognizing the Signs and Immediate Severity
The clinical presentation of SGH is characterized by the rapid development of distinctive physical and systemic signs. The primary physical sign is a progressive, diffuse swelling on the newborn’s scalp that feels soft, or “boggy,” to the touch.
The accumulating blood can spread widely, extending toward the forehead, behind the ears, and down to the neck. In severe cases, the swelling can be so significant that it displaces the earlobes forward or causes bruising around the eyes.
The severity of the condition is directly related to the massive internal blood loss. Because a newborn has a relatively small total blood volume, rapid blood loss into the subgaleal space quickly leads to hypovolemic shock. This shock manifests through systemic signs such as pallor (paleness of the skin) and tachycardia (an abnormally rapid heart rate) as the body attempts to compensate.
As the condition progresses, a newborn will exhibit signs of circulatory failure, including lethargy, diminished muscle tone, and a drop in blood pressure. If not promptly addressed, this acute loss of circulating blood volume can quickly result in organ damage, severe metabolic acidosis, and death. The mortality rate for infants requiring intensive care due to SGH has been reported to be as high as 25% in some studies.
Diagnosis, Medical Management, and Long-Term Outlook
The diagnosis of SGH is often based on clinical suspicion, particularly in an infant who has undergone an assisted delivery and presents with the characteristic diffuse, fluctuant scalp swelling. A healthcare provider will continuously monitor the baby’s vital signs and measure the head circumference hourly to track the bleeding progression. Laboratory tests confirm the degree of blood loss by checking hemoglobin and hematocrit levels, and coagulation studies are performed to check for underlying bleeding disorders.
While the diagnosis is primarily clinical, imaging tests like ultrasound are often used to confirm the blood collection and estimate its size, as this method avoids radiation. Computed tomography (CT) or magnetic resonance imaging (MRI) may be utilized, especially to rule out concurrent intracranial hemorrhages, which occur in a significant percentage of SGH cases.
Immediate medical management focuses on stabilization to counteract hypovolemic shock. This involves volume resuscitation, where fluids are administered intravenously to restore circulating volume. If blood loss is substantial, blood transfusions are given to replace lost red blood cells. Close monitoring in a neonatal intensive care setting is necessary to manage potential complications, including hyperbilirubinemia (jaundice), caused by the breakdown of the accumulated blood.
With timely intervention, the prognosis for most infants who survive the acute phase is favorable. The accumulated blood is reabsorbed by the body over several weeks, and the swelling resolves. While a small number of infants may experience neurological deficits, the long-term outlook for neonatal survivors is good. Ongoing follow-up is necessary to ensure the infant’s development remains on track, especially if the hemorrhage was associated with severe shock or other head injuries.