Injuries to the scalp account for approximately 80% of all birth injuries experienced by babies during the perinatal period.¹ These delicate tissues can be damaged by both the birthing process itself and inadvertently by clinicians during necessary procedures. Most of these injuries are self-limiting and can be managed conservatively; however, some do need immediate recognition and intervention to minimise their impact on the baby. Scalp injuries are classified by the layer of scalp involved, be it skin, subcutaneous connective tissue, subaponeurotic space, or subperiosteal space.

Anatomy of the scalp

The outermost layer of the scalp is the skin, containing sebaceous glands, hair follicles and capillaries. Underlying this is a connective tissue layer, closely adhering to the overlying skin and connecting it to the galea aponeurosis. Deep to the aponeurotic layer is a space, across which valveless emissary veins travel, connecting superficial scalp vessels to the dural venous sinuses and diploic veins that pass through the bony plates of the skull and supply the intracranial structures. The deeper aspect of the subaponeurotic space is bordered by the periosteal membrane, which covers the bones of the skull and represents the lowest layer of the scalp.

Injuries to the skin

As well as providing the cosmetic function of hair growth and participating in temperature control by allowing heat radiation, the skin acts as a physical barrier to infection, which is particularly important in babies, especially if premature. Although uncommon, the skin (and underlying tissue) can be lacerated during caesarean birth and, if the wound is long or deep enough, might require suturing. Despite fetal laceration being a recognised complication of caesarean birth, it is difficult to determine numbers and rates of scalp laceration specifically from current literature, the issue being that scalp lacerations during caesarean are not separated out from either all laceration injuries during operative birth or all scalp injuries related to all birthing methods. Lacerations can also occur with application of both forceps and vacuum cups to the fetal head, and these are often associated with more diffuse injuries to the underlying tissues. However, isolated scalp lacerations are a very uncommon cause of admission to neonatal units, with the majority being small injuries, managed conservatively in maternity wards.

The use of fetal scalp electrodes (FSE) also injures the skin as the anchoring wire passes into the skin and subcutaneous tissue. An early study by Ashkenazi et al.² in 1985 reported an incidence of scalp lacerations of up to 41% in babies with FSE, although the vast majority were transient superficial lacerations that may or may not have been still present at discharge. Severe lacerations with ulceration occurred in 1.3% of their cohort, a figure confirmed more recently in 2016 by a Washington-based group.³ The development of abscesses is well described with FSE use, and more serious infective complications such as osteomyelitis, and epidural and brain abscesses, have also been reported in the literature, illustrating the importance of the skin as a protective barrier.

On occasion, cutis aplasia congenita of the scalp, a congenital defect in the skin (and sometimes the underlying subcutaneous tissue as well), might be mistaken for a scalp injury. If small and superficial, these defects tend to be self-healing, although they might be associated with other abnormalities and their presence should prompt an examination looking for evidence of syndromic features or underlying soft tissue anomalies.⁴

Injuries to the subcutaneous connective tissue

Given the dense structure of this layer, severe injuries involving only this tissue are extremely rare.⁵ It might become infected secondarily following injury to the skin, developing into cellulitis, but the primary injury tends to be either caput succedaneum or a chignon.

Caput succedaneum, commonly known as ‘caput’, is a diffuse, boggy, fluctuant swelling of the scalp, crossing suture lines, and gradually moving dependent on the baby’s position. This oedema within the subcutaneous tissues arises secondary to direct pressure on the affected part of the head from maternal pelvic structures during birth. The fluid is most commonly serous, or haemoserous, and might be associated with the development of jaundice in the baby as the swelling resolves. Instrumental use might also cause caput, and macrosomic babies, those with a longer labour, and those with oligohydramnios also have an increased risk of its development.

Vacuum cup use during birth is particularly associated with scalp swellings, called a chignon. A chignon is more discrete in shape, following the contours of the cup itself and, unlike caput, it does not tend to move based on the baby’s position. There is commonly a larger component of blood in the swelling and a consequent increased likelihood of neonatal jaundice as the erythrocytes in the bruise are broken down. It differs from cephalhaematoma in that it is confined to the location of the vacuum cup, and consequently might cross suture lines. There might be superficial skin lacerations overlying the swelling, which should be observed for healing and for any signs of infection developing, and the baby should be monitored for jaundice, which might require treatment.

Bleeding into the subaponeurotic space

Subaponeurotic or subgaleal haemorrhages have the potential to be life-threatening, and early recognition and appropriate management is vital. The subaponeurotic space is extremely large and provides no natural tamponade to bleeding from the disruption of the emissary veins within the space. Blood loss into this space might be up to 80% of the baby’s circulating volume, resulting in hypovolaemic shock, coagulopathy and death. Given the seriousness of these bleeds, many centres have developed guidelines to assist clinicians in providing support to affected babies, many of which are published online and all are broadly in agreement. It is always useful to be familiar with local guidance for such situations. Although extremely rare in non-instrumental deliveries, these haemorrhages are a recognised complication of instrumental birth, especially with the use of a vacuum cup, and RANZCOG has developed specific guidance on their use and the prevention and detection of subgaleal bleeds.⁶ Recognition of subgaleal haemorrhages can be difficult and most guidelines use an escalating surveillance system for babies at risk of subgaleal haemorrhages, detailing the investigations and assessments required with each level of concern or risk. Clinical features raising suspicion of a subgaleal bleed include a diffuse, fluctuant scalp swelling, which might cross suture lines, might be ballotable, and might demonstrate a fluid thrill, and fluid shift on repositioning the baby. The baby might have features of shock, although a normal heart rate and blood pressure might be falsely reassuring in unwell babies. Key factors in timely management of affected babies include:

• early recognition (based on risk factors, surveillance level and clinical appearance)
• immediate advice from a neonatologist
• not delaying stabilisation by waiting for diagnostic imaging
• aggressive resuscitation, including the use of blood products, to restore circulating volume and correct coagulopathy, and to correct acidosis
• regular reviews of haemodynamic stability and response to resuscitation and stabilisation measures

As with all births, intramuscular vitamin K use should be encouraged, but this is particularly important in instrumental deliveries.

Bleeding into the subperiosteal space

Unlike subgaleal bleeds, bleeding into the subperiosteal space is naturally tamponaded by the boundaries of the specific bony plate affected, resulting in a cephalhaematoma.⁷ These occur when shearing forces during birth strip the periosteum away from the underlying bone, with resultant rupture of blood vessels. Unlike a chignon, these bleeds are commonly not evident at birth, becoming apparent in the first few days of life as a discrete swelling, confined within the suture lines. There is usually no, or minimal, injury to the overlying skin. The swelling is often fairly firm initially, becoming more fluctuant over time. Like swellings in the superficial connective tissue layer, cephalhaematomas are more common in macrosomic babies and those requiring instrumental delivery. There is also an increased incidence in occipitoposterior positioning of the fetus.

Cephalhaematomas commonly require no specific treatment and will resolve spontaneously over a number of weeks. They can become calcified, producing an unusual head shape, but these also resolve, usually within approximately three months. As with other conditions in which bruising occurs, babies are more likely to develop jaundice requiring treatment. They should not be aspirated, because of the risk of introducing infection. Affected babies should be evaluated for bleeding diatheses, such as von Willebrand disease, and some clinicians investigate for associated bony injury, especially if there are concerns for fractures and/or intracranial bleeding.

Summary

Injuries to the neonatal scalp are the most common of all birth injuries. Most of them are self-resolving and require little more than monitoring the affected baby for jaundice; however, development of associated infection, or the presence of a subgaleal haemorrhage, requires early recognition and prompt, definitive action.