The Post-natal Period lasts from birth (usually Week 40 after conception ) to the end of adolesence, around 18 years old. The Post-natal Period can be divided into neonatal, infancy, childhood , and adolescence stages.

Neonatal (Birth-Month 1)

The neonatal stage spans the period from birth to about 1 month. Most of the major bones of the skull are ossified at birth(see Fig. 1 and 2), but can move relative to one another . This mobility of individual skull bones is especially important in childbirth, allowing the bones to overlap and the head to deform during the birthing process. The face, or viscerocranium, at birth comprises only approximately one-eighth of the total head, a ratio which, by adulthood becomes one-half. This change occurs as teeth erupt and the nasal cavity and the maxillary sinuses enlarge during infancy and childhood. In the neonate, the mandible contains ten deciduous teeth and is composed of two halves united by a midline suture. The maxilla also contains ten deciduous teeth.

This ability of the bones to move is permitted by sutures, fibrous membranes that exist between the flat bones of the neurocranium. Sutures permit growth at the edges of the bone. At birth, certain sutures are expanded, creating wide gaps known as fontanelles (seeFig.3).

There are six fontanelles at the edges of the parietal bones:

•   anterior, also referred to as a baby's "soft spot", closed by 2 years
•   2 sphenoidal (anterolateral), closed within 6 months-2 years after birth
  
•   2 mastoidal (posterolateral), closed within 6 months-2 years after birth
  
•   posterior, closed within 6 months-2 years after birth

Clinically, palpation of these areas allows evaluation of normal developmental signs such as hydration, intracranial pressure and bone growth. (England)

Even after visible gaps between the neurocranial bones have been replaced by bone, the fibrous sutures permit additional growth to occur. In normal development, bones that meet at each cranial suture fuse together at different rates that allow for normal expansion of the brain and soft tissues during infancy and childhood. By early adulthood the fusion of all craniofacial sutures are completed.

•   Metopic, or frontal, suture. Separates the frontal bone into two halves.
  
•   Sagittal suture. Separates the two parietal bones and extends from the anterior fontanelle to the posterior fontanelle.
  
•   Coronal suture. Separates the frontal bone from the parietal bone
  
•   Lambdoid suture. Separates the posterior edge of the of the parietal bone form the occipital bone.
  
•   Squamosal suture. Superior border of the squamous part of the temporal bone. Anteriorly, it articulates with the greater wing of the sphenoid; superiorly, it articulates with the parietal bone and posteriorly and inferiorly it articulates with the occipital bone

Premature fusion (craniosynostosis) of any of these sutures creates developmental problems. The cause of craniosynostosis can be multiple. Craniosynostosis is categorized into isolated craniosynostosis and which involves one or more sutures, and syndromic craniosynostosis, conditions that involve synostosis of the skull combined with other facial and bodily anomalies. For more info see our section on Disorders of Development section on craniosynostosis, or check out our Related Links page.

In addition to the cranial sutures are various facial sutures (see Fig.5) that are also points of skull growth and expansion. Major facial sutures include the zygomaxillary, zygotemporal, frontozygomatic, frontomaxillary, nasofrontal, internasal, and intermaxillary sutures. Growth about these sutures, including the many within the orbit, occurs simultaneously with expansion of the cranial sutures, involving an overall displacement of the facial structures (Cohen, 1986).