In plain words
A fontanelle is a soft spot on a baby's head where the skull bones have not yet fused. Babies have a few of them. The largest one, at the top front, usually closes between about 9 and 18 months. The soft spots let the head move through the birth canal and allow the brain to grow. The fontanelle can look slightly sunken or bulging with changes in hydration or with crying, and clinicians check it along with the baby's feeding, alertness, and growth. A soft spot that looks very sunken, or a bulging soft spot with fever, vomiting, or unusual sleepiness, needs a call to your pediatrician right away.
The deeper version
The anterior fontanelle is a membrane-filled diamond-shaped gap between the frontal and parietal bones, typically closing between 9 and 18 months. The posterior fontanelle closes by about 2 months. Fontanelle assessment, along with head circumference percentiles and neurologic examination, is part of infant surveillance. A sunken fontanelle suggests dehydration, and a tense or bulging one may indicate raised intracranial pressure, meningitis, or other pathology. Early fusion of sutures, craniosynostosis, is assessed by suture palpation and head shape. Clinical guidance is set out in the AAP periodicity schedule.
Where it comes up
- Tummy timeBaby Basics
- When to call the pediatrician (and when to go in)Baby Basics
- Newborn procedures: vitamin K, eye ointment, hepatitis B, screeningGetting Ready for Birth
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Sources
- American Academy of Pediatrics — Bright Futures Guidelines for Health Supervision of Infants, Children, and Adolescents, 4th edition, 2017