A baby's skull doesn't fully close at one specific age, but rather in stages, with the soft spots (fontanelles) gradually closing. The last of these to close typically does so by 18 months old.
Understanding Fontanelles
Fontanelles are the soft, membranous gaps between the bones of a baby's skull. These spaces are crucial for allowing the baby's brain to grow rapidly during the first year of life and for making childbirth easier. There are two main fontanelles:
- Posterior Fontanelle: This is located at the back of the head. It's the smaller of the two and usually closes first.
- Anterior Fontanelle: This is located on the top of the head. It's larger and takes longer to close.
Closure Timeline
Here's a breakdown of when the fontanelles typically close, as indicated by the provided reference:
| Fontanelle | Closure Time |
|---|---|
| Posterior Fontanelle | Within 2 months of birth |
| Anterior Fontanelle | Between 7 and 18 months |
As the table shows, the posterior fontanelle closes relatively quickly after birth, usually within the first two months. The anterior fontanelle, on the other hand, can take a bit longer, typically closing sometime between 7 and 18 months of age. Therefore, we can conclude that the skull is fully closed when the anterior fontanelle closes, which happens by the time a baby is 18 months old.
Practical Implications
- Palpating: Doctors check fontanelles during routine checkups. This allows them to assess the baby’s health and development.
- Safety: While the fontanelles are soft, the membrane covering them is very tough, and touching them is generally not harmful.
- Consult a Doctor: If you notice any unusual bulging or depression of a fontanelle, or if it is not closing as expected, consult your pediatrician.
By 18 months, the skull is typically fully closed, providing a solid protective structure for the brain.
