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Fontanelles are membrane-covered 'soft spots' in the spaces where two sutures in the fetal skill join together. They allow for growth of the brain and skull during the baby's first year of life.
The posterior fontanelle usually closes by the time the baby is 1 - 2 months old. The anterior fontanel usually closes between 7 and 19 months.
Fontanelles should feel firm and very slightly curved inward to the touch. A tense or bulging fontanelle may indicate increased intracranial pressure. Possible causes include encephalitis, hydrocephalus, or meningitis.
A sunken fontanelle may indicate dehydration or malnutrition.
Midwives should check the size and tension of the fontanelles as part of a discharge examination, which should include occipital frontal circumference (OFC), suture lines, cranial moulding, caput succedaneum and cephalhaematoma. Any abnormalities should be reported to a senior paediatrician and documented in the baby's case notes.