Diploma in Midwifery

The Fetal Skull

Table of Contents

 The fetal skull is a protective bony structure that encases the delicate brain within the head. This bony compartment is crucial as it shields the brain from potential harm, particularly during the birthing process.

 

The way the fetal head is positioned during normal labor is of significant importance. A successful delivery of the head is a prerequisite for the subsequent and easier delivery of the rest of the fetal body. 

The structure of the fetal skull is characterized by a degree of flexibility and compressibility. It is largely composed of thin, flexible, plate-like (flat) bones that form the cranial vault. These bones are connected to the solid and rigid bones located at the base of the skull.

Divisions of the Fetal Head:

Face: This section of the fetal skull comprises 14 bones, which originate from cartilage. At the time of birth, these facial bones are almost completely ossified (hardened), fused together, and provide a robust protective layer for the brain. The facial region is defined as the area extending from the bony ridges above the eyes (orbital ridges) down to the junction between the chin and neck.

Base: The base of the fetal skull is made up of firmly joined bones which serve to protect essential control centers within the brain. There are five bones in total within the base, and like the facial bones, they develop from cartilage and are fully ossified at birth, contributing to a strong foundation.

Vault: The vault refers to the upper and larger portion of the fetal skull. It is defined as the area situated above an imaginary line drawn from the nape of the neck to the orbital ridges (eye socket rims). This is typically the largest diameter of the fetal head and is usually the first part to navigate through the birth canal during labor. The bones of the vault develop from membranes, which allows for some flexibility during birth.

Fetal skull showing different regions and landmarks of obstetrical significance

Sinciput and Occiput:

The sinciput refers to the region located in front of the anterior fontanelle, corresponding to the area of the brow. Conversely, the occiput is specifically defined as the area occupied by the occipital bone at the back of the skull.

The flat bones that constitute the vault are joined together by unossified membranous tissues at their edges. These membranous junctions are known as sutures and fontanelles. Among the numerous sutures and fontanelles present in the fetal skull, specific ones hold particular significance in obstetrics.

Bones of the Vault of the Fetal Skull:

The bony framework of the vault originates from within a membranous structure. Over time, a process of bone formation, called ossification, occurs, hardening these structures starting from central points and spreading outwards.

At birth, this ossification process is still incomplete. Consequently, small gaps persist between the bones, forming what are known as sutures and fontanelles. Each individual bone has a primary ossification center, which often presents as a noticeable bump or prominence. The skull doesn’t achieve complete ossification until early adulthood.

The bony components of the vault include:

(i) Frontal Bones (Two): These bones form the forehead area, also termed the sinciput. Each frontal bone possesses a primary ossification center, resulting in a frontal eminence (brow ridge). Initially paired and somewhat square-shaped, these bones typically fuse to become a single frontal bone by approximately 8 years of age.

(ii) Parietal Bones (Two): Situated on either side of the skull, these bones form the sides and roof of the cranial vault. Each parietal bone also has its own ossification center, creating a parietal eminence (parietal boss). They are generally rectangular in shape.

(iii) Occipital Bone: Located at the rear of the head, the occipital bone has a portion that contributes to the skull’s base. Importantly, it contains the foramen magnum, a large opening that allows passage of the spinal cord, thus providing crucial protection. This bone is triangular in shape, and its ossification center manifests as the occipital protuberance (external occipital protuberance).

(iv) Temporal Bones (Upper Segments – Two): The upper portions of the temporal bones, located on each side of the head, contribute to the structural formation of the vault on both sides.

Development of the Vault:

Within the membranes, five primary ossification centers emerge, initiating the process of calcium deposition and bone formation (ossification). Specialized cells, chondrocytes, play a role in the development of these membranes. These ossification centers give rise to noticeable prominences on the skull’s surface, such as the frontal bosses, parietal eminences, and the occipital protuberance.

Clinical Considerations:

  1. Premature Infants: In babies born prematurely, the bones of the vault are less ossified, leaving larger membranous spaces. This reduced bony support makes premature infants more vulnerable to intracranial injuries during delivery.

  2. Full-Term Infants: At full term, while ossification is more advanced, narrow membranous areas still persist. These areas allow for a degree of molding – the bones can slightly overlap – during labor. This molding process is beneficial as it allows the fetal head to adapt its shape and navigate the birth canal more easily.

  3. Post-Mature Infants: In infants born post-term, ossification progresses further. This results in harder skull bones and narrower membranous spaces, reducing the capacity for molding. Consequently, delivery can become more challenging, and there’s an increased risk of intracranial injury due to the reduced ability of the head to adapt to the birth canal.

Regions of the Fetal Skull:

The fetal skull is further categorized into distinct sections, each defined by specific anatomical landmarks (as illustrated in the preceding diagram). These reference points are clinically important, especially for midwives during vaginal examinations, as they help in determining the position of the fetal head during labor.

(i) Vertex: This area is located between the anterior fontanelle (situated at the front of the skull), the posterior fontanelle (at the rear), and the two parietal eminences (on the sides of the skull). The vertex presentation is the most frequent fetal position during childbirth, occurring in approximately 95% of deliveries.

(ii) Sinciput (Brow): This region extends from the anterior fontanelle and the coronal suture (a line where skull bones join) to the bony ridges above the eye sockets, known as the orbital ridges.

(iii) Face: The facial region spans from the orbital ridges and the root of the nose down to the point where the chin meets the neck. The chin itself, also called the mentum, is a significant landmark within this area. It is worth noting that the face is proportionately smaller in newborn infants. The area situated between the eyebrows is specifically termed the glabella.

(iv) Occiput: This region is positioned between the foramen magnum (the large opening at the base of the skull) and the posterior fontanelle. The area immediately below the occipital protuberance (a prominent bony landmark) is designated as the suboccipital region. The occipital protuberance is a noticeable projection on the posterior (back) surface of the skull.

SUTURES

Sutures are fibrous bands or lines that represent the joints between the bones of the fetal cranium. These specialized connections are composed of membrane and permit a degree of bone movement at these junctions. This mobility is crucial, particularly during childbirth, as it allows for slight overlapping of the skull bones.

Important Sutures in Obstetrics:

Frontal (Metopic) Suture: This suture is situated between the two halves of the frontal bone. It is also known as the metopic suture and is notable for typically fusing and becoming less distinct as the individual grows.

Coronal Suture: This suture marks the boundary between the frontal bone (at the front of the skull) and the parietal bones (which form the sides and roof of the cranium).

Sagittal Suture: Located on the top of the skull, this suture runs lengthwise, separating the two parietal bones from each other.

Lambdoid Suture: This suture defines the junction between the occipital bone (at the back of the skull) and the parietal bones.

Squamous Suture: Positioned on the sides of the skull, this suture separates the temporal bone (located at the temple) from the parietal bone.

Importance:

  1. Facilitating Cranial Molding: The sutures enable a controlled degree of movement between the skull bones. This is essential for a process called molding, where the bones can slightly slide over one another. Molding is vital as it allows the fetal head to reduce its diameter and adapt its shape, thereby easing its passage through the maternal pelvis during labor.

  2. Obstetrical Assessment: During a vaginal examination in labor, feeling (palpating) the sagittal suture provides valuable clinical information. It can assist in determining whether the fetal head is properly engaged in the pelvis (synclitism or asynclitism – referring to whether the head is entering the pelvis straight or tilted), the extent of the baby’s head rotation as it descends through the birth canal, and the degree of molding that has occurred.

FONTANELS

Fontanelles are areas within the fetal skull where multiple sutures intersect, creating membranous gaps. These spaces are crucial because they allow for skull molding during childbirth, enabling the head to navigate the birth canal.

While there are several fontanelles in total (typically six), two are particularly significant in obstetrics: the anterior fontanelle (bregma) and the posterior fontanelle (lambda).

Anterior Fontanelle: This fontanelle arises at the meeting point of four sutures in the midline of the skull. These sutures are the frontal suture at the front, the sagittal suture behind it, and the coronal sutures on each side. It has a characteristic diamond shape and is approximately 3 cm in both anteroposterior (front-to-back) and transverse (side-to-side) dimensions. The base of the anterior fontanelle is made of a membrane that progressively ossifies (turns to bone) usually around 18 months after birth. Delayed ossification beyond 24 months might indicate an underlying issue.

Importance:

  • Assessing Head Flexion: During a vaginal examination, feeling the anterior fontanelle can provide information about the degree of flexion of the fetal head.

  • Facilitating Molding: It plays a key role in allowing the skull bones to mold and overlap during labor.

  • Brain Growth Accommodation: The persistent membranous nature after birth allows space for significant brain growth during the first year of life when the brain nearly doubles in size.

  • Reflecting Intracranial Conditions: Palpation of the fontanelle’s membrane can offer clues about the baby’s internal condition – for instance, a sunken fontanelle may suggest dehydration, while a bulging one might indicate increased pressure within the skull.

  • Medical Access (Rare): In rare and emergency situations, the anterior fontanelle, via the superior longitudinal sinus, can be used for procedures like blood collection or exchange transfusions. Cerebrospinal fluid can also be accessed from the lateral ventricle through the angle of the anterior fontanelle, though this is also uncommon.

Posterior Fontanelle: This fontanelle is formed where three sutures come together: the sagittal suture in front and the lambdoid sutures on either side. It has a triangular shape and is smaller than the anterior fontanelle, measuring roughly 1.2 cm by 1.2 cm. Although described as membranous, its base tends to become more bony around the time of birth. Therefore, calling it a ‘fontanelle’ in the strict sense may be slightly inaccurate at term.

Importance:

  • Head Position Indicator: The posterior fontanelle’s position helps to determine the orientation of the fetal head in relation to the mother’s pelvis during labor.

Sagittal Fontanelle: This fontanelle is not consistently present. When it does occur, it is located along the sagittal suture, approximately at the junction of the front two-thirds and back one-third of the suture. It is considered to have no significant clinical relevance in obstetrics.

Diameters of the Fetal Skull:

The diameter of the fetal skull that engages (enters) the maternal pelvis is determined by the extent to which the fetal head is flexed (chin tucked towards the chest). The anteroposterior (front-to-back) diameters of the fetal head that are relevant during labor and delivery include:

Diameters of the Fetal Skull

The diameter of the fetal skull that presents during birth is influenced by the degree of head flexion. Here are the anteroposterior diameters relevant to engagement:

PresentationDiameter(cm)Attitude of the Head
VertexSuboccipitobregmatic9.5Complete flexion
VertexSuboccipito-frontal10Incomplete flexion
VertexOccupitofrontal11.5Marked deflexion
BrowMento-vertical13.5Partial extension
FaceSubmentovertical11.5Incomplete extension
FaceSubmentobregmatic9.5Complete extension

Diameters are classified as transverse and longitudinal:

(i) Transverse Diameters:

Bi-Parietal Diameter: This measurement represents the distance between the two parietal eminences, the widest points on the parietal bones, typically around 9.5 centimeters.

Bi-Temporal Diameter: This diameter is the measurement across the skull at its widest points along the coronal suture, approximately 8.2 centimeters in width.

(ii) Longitudinal Diameters: These measurements are taken along the length of the fetal skull from different anatomical points. They are crucial for understanding the fetal head’s position and how easily it can pass through the birth canal.

Suboccipito-Bregmatic Diameter: Measured from just beneath the occipital protuberance (the bump at the back of the head) to the center of the anterior fontanelle. This is often the smallest front-to-back diameter of the fetal head, measuring about 9.5 centimeters, and is generally considered favorable for vaginal birth.

Suboccipito-Frontal Diameter: Extends from below the occipital protuberance to the midpoint of the frontal suture (located on the forehead). This diameter measures approximately 10 centimeters.

Occipito-Frontal Diameter: This measurement is taken from the occipital protuberance to the glabella, which is the smooth area on the forehead between the eyebrows. Its length is around 11.5 centimeters.

Mentovertical Diameter: The longest diameter of the fetal head, stretching from the tip of the chin (mentum) to the highest point of the vertex (top of the head). This measures about 13.5 centimeters. This diameter is typically presented when the baby’s head is in a brow presentation, which can make vaginal delivery significantly more difficult or sometimes impossible.

Submento-Bregmatic Diameter: Measured from the point where the chin meets the neck to the bregma (anterior fontanelle). This diameter is approximately 9.5 centimeters.

Submento-Vertical Diameter: Extends from the junction of the chin and neck to the highest point on the vertex of the skull. This measurement is around 11.5 centimeters.

Summary of Diameters in Different Presentations

DiameterLengthPresentation
Suboccipito-bregmatic9.5cmVertex (Complete Flexion)
Submentobregmatic9.5cmFace (Complete Extension)
Suboccipito-frontal10.5cmVertex (Incomplete Flexion)
Occipitofrontal11.5cmVertex (Marked Deflexion)
Submentovertical11.5cmFace (Incomplete Extension)
Mento-vertical13.5-14 cmBrow (Partial Extension)
Transverse Diameters

Regarding the breadth of the fetal skull, there are two key transverse measurements to consider:

  • Biparietal Diameter (approximately 9.5 cm): This represents the widest span of the fetal head from side to side. It is the measurement taken between the parietal eminences, which are the most prominent points on each parietal bone.

  • Bitemporal Diameter (approximately 8.2 cm): This measurement indicates the width of the fetal head across the temples. Specifically, it is the distance between the two most distant points of the coronal suture as it runs across the temporal regions of the skull.

  •  

Fetal Trunk Diameters

Understanding the dimensions of the fetal trunk is also crucial, particularly for the delivery of the shoulders and in breech presentations.

  • Bisacromial Diameter (approximately 12 cm): This diameter is the distance between the acromion processes, bony projections on the shoulder blades. It is the widest dimension of the fetal shoulders and must pass through the pelvic inlet during birth of the shoulders. The clavicles’ articulation with the sternum provides some flexibility, allowing the shoulders to move forward and potentially reduce this diameter slightly during delivery.

  • Bitrochanteric Diameter (approximately 10 cm): This measurement is taken between the greater trochanters, which are prominent bony points on the upper femurs (thigh bones). In a breech presentation, where the baby’s buttocks and legs present first, this diameter is the presenting dimension that must navigate the maternal pelvis.

ATTITUDE OF THE FETAL HEAD

The attitude of the fetal head describes the degree to which the baby’s head is bent forward (flexed) or backward (extended) in relation to its body.

This head position is critically important because it directly determines which diameter of the fetal skull will be positioned to enter the pelvis during labor. This, in turn, significantly affects how labor progresses and ultimately the outcome of delivery.

When the fetal head is well-flexed (chin tucked down towards the chest), the smaller diameters of the skull are presented. This more compact presentation makes it easier for the baby’s head to pass through the birth canal.

In contrast, if the fetal head is extended (tilted back), larger diameters of the skull are presented to the pelvis. This larger profile can potentially lead to difficulties and complications during labor.

Presenting Diameters vs. Engaging Diameters:

It is essential to distinguish between two terms used when discussing fetal head diameters in labor:

Presenting Diameters: These refer to the diameters of the fetal skull that are initially positioned perpendicular to the curve of Carus. The curve of Carus represents the general direction of the birth canal. Presenting diameters are important for identifying the baby’s initial presentation and the orientation (lie) of the head before it enters the pelvis.

Engaging Diameters: These are the diameters that become relevant after the fetal head has flexed appropriately and begun its descent into the pelvic inlet (brim). These are the diameters that will actually stretch and put pressure on the perineum during the second stage of labor (pushing stage). Both longitudinal and transverse diameters can act as engaging diameters, depending on the fetal head’s position and flexion.

Presenting/Engaging Diameters in Different Presentations:

The suitability of presenting diameters for navigating the maternal pelvis varies, significantly influenced by the fetal head’s attitude. This attitude, referring to the degree of flexion or extension of the fetal head upon the neck, is paramount in determining which skull diameters will present during labor, thereby impacting the labor’s progression and eventual outcome.

Presenting diameters are defined as those fetal skull dimensions positioned at right angles to the curve of Carus within the maternal pelvis. In every scenario, there will be both a longitudinal and a transverse diameter presenting. These presenting diameters ultimately dictate the fetal head presentation, categorized primarily into three types. The fetal head’s attitude fundamentally determines which diameters will become the engaging diameters as labor progresses.

  1. Vertex Presentation (Optimal):

In a vertex presentation, the fetal head is ideally flexed, with the chin brought towards the chest. This attitude results in the engagement of the suboccipito-bregmatic diameter (approximately 9.5cm) and the biparietal diameter (approximately 9.5cm). Due to their near-equal measurements, the area presented to the pelvic inlet assumes a roughly circular configuration, which is highly advantageous for cervical dilation and subsequent passage of the head. This configuration presents an area with a circumference of approximately 29cm. This reduced circumference is optimally suited for facilitating cervical effacement and dilation, leading to a more straightforward vaginal delivery as it minimizes the stress on the birth canal tissues. The sub-occipitofrontal diameter (around 10 cm) is the dimension that expands the vaginal opening during delivery. Conversely, should the head become deflexed, the presenting diameters shift to the occipitofrontal (approximately 11.5 cm) and the biparietal (approximately 9.5 cm). This often occurs when the occiput is positioned posteriorly. In such persistent posterior positions, the occipitofrontal diameter (11.5 cm) is likely to be the dimension responsible for dilating the vaginal opening.

  1. Brow Presentation (Difficult):

A brow presentation occurs when the fetal head is in a state of partial extension, causing the brow to be the leading part. This partial extension results in the mentovertical diameter (approximately 13.5 cm) and the bitemporal diameter (approximately 8.2 cm) becoming the presenting diameters. These dimensions are considerably larger compared to those in vertex presentations. The head circumference in this presentation approximates 38cm. Due to these increased diameters, engagement into the pelvis is frequently challenging, and vaginal delivery is often deemed unachievable. Consequently, a Cesarean section is often the necessary course of action.

  1. Face Presentation (Challenging):

In a face presentation, the fetal head is completely extended, leading to the face presenting first. In this scenario, the submento-bregmatic diameter (approximately 9.5cm) engages with the pelvis. While this diameter is comparatively smaller, labor in face presentation still tends to be more complicated. This increased difficulty arises from the facial bones exhibiting less malleability, meaning they do not mold and reshape as readily as the vault bones of the cranium. Although vaginal delivery might be achievable in certain circumstances, it is generally considered to be a more complex process and may necessitate obstetric interventions.

Summary:

The attitude of the fetal head is a pivotal determinant in the progression of labor. Optimal flexion, resulting in a vertex presentation, leads to the presentation of smaller skull diameters. This facilitates a more efficient passage through the birth canal. Conversely, extension, observed in brow and face presentations, presents larger diameters, which significantly elevates the complexity and risks associated with vaginal delivery. A thorough understanding of the interrelation between fetal head attitude, presenting diameters, and the maternal pelvis is indispensable for ensuring safe and effective obstetrical management.

Examination of the Parts of the Fetal Skull

Task: Description of the sutures and fontanelles.

Objectives:

  1. To identify the sutures and fontanelles.

  2. To explain the importance of fontanelles.

Requirements:

A flat surface
A fetal skull

MOULDING

The term moulding describes the alteration in the shape of the baby’s head as it journeys through the birth passage during labor. This reshaping is a natural and beneficial adaptation that facilitates the birth process.

This change in head shape is made possible due to the inherent flexibility of the cranial bones forming the vault. These bones can bend slightly, and importantly, they are capable of overlapping at the suture lines – the junctions between the bones. This overlapping, also known as overriding, allows for a notable decrease in the skull’s presenting diameters. Simultaneously, the diameter positioned at a right angle to this shortening can expand slightly, accommodated by the flexibility inherent in the skull bones.

This reduction in fetal head diameters through moulding can be significant, potentially reaching up to 1.25 cm. Moulding is not only an adaptation for easier passage, but it also acts as a safeguarding mechanism. It helps to shield the delicate fetal brain from excessive compression during birth, provided that the moulding is not too extreme, too rapid, or occurring in an unfavorable direction. It is important to note that the skull of a baby born prematurely has bones that are softer and sutures that are wider compared to a baby born at full term. Consequently, preterm infants are more susceptible to excessive moulding if labor occurs before their due date.

The Process of Molding:

Moulding occurs through the overlapping of the bones that make up the fetal skull along their suture lines. Specifically, the frontal bone is maneuvered to slide beneath the forward portion of the parietal bones. Concurrently, the occipital bone is positioned to slide under the rearward section of the parietal bones. Furthermore, the two parietal bones themselves also shift to overlap each other. This intricate process effectively reduces the overall dimensions of the fetal head.

Principles of Molding:

  1. Reduction of Engaging Diameter: The diameter of the fetal head that is initially presented to the pelvis is subjected to pressure from the pelvic structures, causing it to decrease in length.

  2. Elongation of Perpendicular Diameter: The diameter of the fetal head that is oriented at a right angle to the engaging diameter compensates by increasing in length.

  3. Frontal Bone Movement: At the coronal suture line, the frontal bones are directed to slide beneath the overlying parietal bones.

  4. Occipital Bone Movement: At the lambdoid suture line, the occipital bone is guided to move under the parietal bones.

  5. Parietal Bone Overlap: The two parietal bones adjust their position to overlap each other along the sagittal suture.

Collectively, these actions result in a reduction of approximately 1.25cm in the engaging diameter of the fetal head.

In summary,

The primary effect of moulding is to lessen the engaging diameter of the fetal skull – the dimension that initially enters the birth canal – by about 1.25 cm. At the same time, the diameter positioned at a right angle to this engaging diameter experiences an increase in its length. As an example, during a vertex presentation where the head is fully flexed (in a left or right occipitoanterior position), the suboccipito-bregmatic diameter, which is typically 9.5 cm, is shortened, while the mentovertical diameter, normally 13.5 cm, becomes elongated.v

Types of Molding:

  1. Normal Molding:

    • Typically observed in vertex presentations where the baby’s head is well-flexed.

    • Develops gradually, usually over the course of 8 to 18 hours of labor.

    • Characterized by a reduction in the suboccipito-bregmatic diameter of the fetal skull.

    • Considered a physiological and benign process that typically resolves naturally within one to two days after birth.

    • Is a beneficial adaptation as it facilitates vaginal delivery by allowing the fetal head to conform to the shape of the birth canal.

  2. Abnormal Molding:

    Several variations of abnormal moulding are recognized:

    (a) Upward Molding (Sugar Loaf Molding):

    • Often occurs in occiput posterior positions (where the back of the baby’s head is towards the mother’s back) and in breech deliveries, particularly with the after-coming head (head delivered last in breech).

    • Involves an upward traction force on the falx cerebri, a fold of dura mater that separates the two cerebral hemispheres. This upward pull can potentially lead to tearing of the tentorium cerebri, another dural fold, at its junction with the falx cerebri.

    • Tearing in this area is concerning as it can involve major blood vessels such as the great vein of Galen, potentially leading to intracranial hemorrhage.

    • Upward molding is notably associated with deflexed fetal heads during vertex presentations, where the head is not ideally flexed.

    (b) Excessive Molding:

    • Follows the same overlapping pattern as normal molding, but is more pronounced and extreme in its degree.

    • Typically a result of prolonged labor, often due to cephalopelvic disproportion, where there’s a mismatch between the size of the baby’s head and the dimensions of the mother’s pelvis.

    • Other contributing factors include prematurity. Premature infants have softer skull bones and wider sutures and fontanelles, which offer less resistance to molding, potentially leading to excessive deformation.

    • Various other factors that prolong labor can also contribute to excessive molding.

    (c) Rapid Molding:

    • Characterized by a swift compression of the fetal head.

    • Commonly observed in breech deliveries, where the after-coming head traverses the birth canal rapidly, often within a very short timeframe (e.g., 9 minutes). It also occurs in precipitate labor, which is defined as labor that progresses exceptionally quickly, lasting less than 3 hours from onset to delivery.

    • While there may be temporary overlapping of skull bones, significant visible moulding might not be readily apparent due to the speed of delivery.

    • Despite the lack of obvious external signs, rapid molding carries a potential risk of cerebral damage due to the sudden and forceful compression experienced by the fetal brain.

Absence of Molding:

Moulding does not typically occur in the following situations:

  • Elective Cesarean Deliveries: When a Cesarean section is performed by choice before labor begins, the baby’s head does not descend through the birth canal. Consequently, the compressive forces that lead to moulding are absent in these deliveries.

  • Post-term Pregnancies: In pregnancies that extend beyond the due date (post-mature), the sutures of the fetal skull tend to become significantly narrowed or even closed. This advanced stage of ossification reduces the pliability of the skull bones, thus limiting or preventing the occurrence of moulding.

Important Notes on Molding:

  1. Cause of Molding: Moulding is a direct result of sustained compression of the fetal skull. This pressure is exerted on the head as it progresses through the bony confines of the maternal birth canal during vaginal delivery.

  2. Facilitation of Delivery: The primary benefit of moulding is that it effectively reduces the overall diameter of the fetal head. This reduction in size is crucial as it enables the head to navigate the birth canal more easily, thereby facilitating vaginal delivery.

  3. Rigidity of Facial Bones: It is important to note that the bones of the fetal face, in contrast to the vault bones, do not exhibit moulding. This is because the facial bones are more rigidly structured and lack the capacity to overlap or reshape during birth.

  4. Diagnostic Significance: The pattern and degree of moulding observed in a newborn’s head can be clinically informative. It is possible to assess and categorize the type of moulding that has occurred, which can provide insights into the labor process and potentially identify any complications.

  5. Prevalence in Vaginal Births: Some degree of moulding is a common finding in nearly all babies born via vaginal delivery. The exception to this is babies delivered through Cesarean section, where moulding typically does not occur due to the absence of vaginal passage.

Revision Questions.

  1. Define what the fetal skull is.

  2. Describe the different bones that compose the fetal skull.

  3. Identify four significant landmarks on the fetal skull.

  4. Describe the various longitudinal diameters of the fetal skull and their measurements.

  5. Describe the anatomical characteristics of the bregma and lambda.

  6. Outline three important functions of fontanelles and sutures in the fetal skull.

  7. List three distinguishing differences between the anterior and posterior fontanelle.

  8. Define the term ‘moulding’ in the context of fetal head changes during birth.

  9. Explain the physiological process of moulding.

  10. State the underlying principle that governs the moulding process.

  11. Explain and differentiate between three distinct types of abnormal moulding.

Examining the Baby’s Head: A Clinical Procedure
Scenario: A mother has delivered her baby. Examine the baby’s head.
Objectives:
1. To prepare the necessary equipment for the examination.
2. To systematically examine the baby’s head.

table 

Equipment Required for Examination

ItemPurpose
Tape measureMeasure head circumference
Weighing scaleMeasure baby’s weight
ReceiverCollect any waste
ApronProtect clothing
GlovesMaintain hygiene
Adequate lightEnsure clear visibility
Gallipot with cotton swabsClean baby’s head
Baby’s clothesDress the baby after examination
Baby’s chartRecord findings
Firm, flat surfaceProvide a stable examination area
Examination Procedure
 
StepActionRationale
1Use appropriate communication skills when explaining the procedure to the mother.To build a positive relationship and ensure understanding.
2Close nearby windows.To prevent hypothermia (the baby losing body heat).
3Wash hands and put on gloves.To prevent the spread of infections.
4Expose the baby’s head by removing any coverings.To allow for a clear view during the examination.
5Examine the head for size, shape, and symmetry.To rule out prematurity or any abnormalities.
6Palpate the fontanelles and sutures.To rule out bulging fontanelles or other issues.
7Measure the head circumference (33-35cm). 
8Observe the appearance of the face, noting any asymmetry or unusual features.To exclude paralysis or other neurological conditions.
9Examine the eyes, noting any discharge, conjunctival hemorrhage, eye setting, eye color, and response to light. 
10Examine the nose. 
11Examine the mouth for color, presence of thrush, and palpate the hard and soft palate. Examine the tongue for size and presence of a tongue tie. 
12Examine the ears for presence of cartilage.To rule out immaturity or ear deformities.
13Gently turn the baby’s neck and palpate for any masses.To avoid injury and to check for neck abnormalities.
14Place a cup on the baby’s head to make them comfortable and warm.To provide warmth and comfort to the baby.
15Share your findings with the mother.To keep the mother informed about the baby’s health.
16Clear away, wash hands, and record findings.To maintain a clean environment and ensure proper documentation.
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