An essential feature of mammals and particularly primates is the marked increase in brain volume that occurs following delivery. Head circumference increases from 35 cm at birth to 50 cm by age 3 yrs (average adult head circumference is just 5 cm more). This dramatic postnatal brain volume growth requires that the bones not be fused at birth to facilitate vaginal delivery and that fusion of cranial sutures occurs after age 2 yrs. Accordingly, premature fusion of cranial sutures may have an effect on cranial shape and less frequently on brain growth (primary craniosynostosis).
Abnormalities of head shape are a frequent concern of parents, particularly since the infant head is relatively larger than the adult head. Appropriate recognition and evaluation is important to manage craniosynostosis.