The soft spots on a baby’s head, known as fontanelles, allow for brain development and flexibility during birth. These areas are important as their skull is still forming. Understanding their purpose helps parents care for their infant.
What Are Soft Spots?
A baby’s skull is not a single, solid bone at birth; instead, it is composed of several bony plates connected by fibrous joints called sutures. Fontanelles are the gaps covered by tough membranes where these skull bones have not yet fused.
There are typically six fontanelles, but the two most noticeable ones are the anterior and posterior fontanelles. The anterior fontanelle, located on the top-front of the head, is the larger, diamond-shaped soft spot. The posterior fontanelle is smaller, triangular, and found towards the back of the head.
These flexible areas serve two functions. During vaginal birth, fontanelles allow the skull bones to overlap and compress, enabling the baby’s head to navigate the narrow birth canal. After birth, they accommodate the rapid brain growth during the first year of life. The tough membrane covering them protects the underlying brain tissue.
The Closure Timeline
Fontanelle closure occurs at different times as the skull bones gradually fuse. The posterior fontanelle typically closes first, usually within 2 to 3 months after birth, sometimes as early as 6 to 8 weeks. It may be closed at birth or soon after.
The anterior fontanelle, being larger, takes longer to close. It generally closes between 7 and 18 months of age, though it can remain open until 24 months. Male infants’ anterior fontanelles may close sooner than female infants.
When to Be Concerned
While fontanelle closure follows general timelines, certain deviations can indicate underlying health conditions, warranting medical evaluation.
If a fontanelle closes too early, particularly the anterior fontanelle, it can signal craniosynostosis. This condition involves the premature fusion of skull sutures, which can restrict brain growth and lead to an abnormally shaped head. Early closure can also be associated with hyperthyroidism or hyperparathyroidism.
Conversely, a delayed or abnormally large fontanelle closure can also indicate medical issues. Common causes include congenital hypothyroidism, rickets (a condition affecting bone development), Down syndrome, and increased pressure inside the brain. Less common causes include achondroplasia or other genetic conditions.
The fontanelle’s appearance can signal concerns. A bulging fontanelle, especially when the baby is calm, may indicate increased intracranial pressure. This can be a symptom of conditions such as hydrocephalus (fluid buildup in the brain), meningitis (inflammation of brain and spinal cord membranes), encephalitis (brain inflammation), or cerebral hemorrhage. Immediate medical attention is necessary if a bulging fontanelle is observed, particularly if accompanied by vomiting or lethargy.
On the other hand, a sunken fontanelle often suggests dehydration. If a baby’s soft spot appears noticeably sunken, it indicates insufficient fluid intake. This can occur due to vomiting or diarrhea. Other signs of dehydration, such as fewer wet diapers or a dry mouth, usually accompany a sunken fontanelle. Prompt medical consultation is advised for any concerns regarding the fontanelles’ appearance or closure.
Caring for Your Baby’s Soft Spot
Parents often feel anxious about touching their baby’s soft spots, fearing harm. However, fontanelles are covered by a tough, protective membrane, making them less fragile than they appear. Gentle contact during daily activities is safe and will not injure the baby’s brain.
Routine care, such as washing the baby’s hair and scalp, can be performed gently over the fontanelle area. Using a soft baby brush or comb and putting on hats or headbands are also safe. While gentle handling is fine, direct pressure or forceful impact should be avoided. Supporting the baby’s head and neck, especially in the early months, helps protect this developing area.