The “soft spot” on a baby’s head, medically known as a fontanelle, is a normal part of infant development. These unfused skull bones are present at birth and play a significant role in a baby’s growth. Understanding fontanelles is key for new parents to appreciate their importance and how to care for their infant.
Anatomy and Purpose of the Soft Spots
A baby’s skull is not a single, solid bone at birth; instead, it is composed of several bony plates joined by flexible, fibrous tissues called sutures. The gaps where these sutures meet create the “soft spots” or fontanelles. While there are typically six fontanelles present in infancy, the two most prominent are the anterior and posterior fontanelles. The anterior fontanelle, often referred to as the main soft spot, is diamond-shaped and located on the top of the head, between the two frontal and two parietal bones. The posterior fontanelle is smaller, triangular, and found at the back of the head, where the two parietal bones meet the occipital bone.
These unfused areas and flexible sutures serve two primary functions related to birth and early development. During vaginal delivery, fontanelles allow skull plates to overlap and flex, enabling the baby’s head to mold and pass through the birth canal. This temporary change protects the brain from pressure. Following birth, fontanelles are essential for accommodating the rapid growth of the infant’s brain. The brain grows significantly during the first year, and open fontanelles allow the skull to expand, preventing restricted development.
Care and Observation
Caring for a baby’s head, even with the presence of soft spots, is straightforward and does not require excessive caution beyond typical infant handling. The fontanelles are covered by tough, protective membranes, meaning gentle touching, washing the baby’s hair, or normal everyday activities will not harm the brain. Parents can gently run their fingers over the fontanelles without concern.
A normal fontanelle appears flat or slightly curved inward and feels soft. A slight pulsation (blood flow) is common, as is a slightly raised appearance when a baby cries, coughs, or vomits. However, certain changes warrant medical attention. A bulging fontanelle that remains raised could indicate increased pressure inside the skull, possibly due to fluid buildup or swelling. Conversely, a noticeably sunken fontanelle may signal dehydration; unusual size or closure much earlier or later than expected also warrant pediatrician evaluation.
Closure Timeline
The fontanelles close as the skull bones gradually grow and fuse together, a process known as ossification. This closure occurs at different times for each fontanelle. The posterior fontanelle, located at the back of the head, closes first. It is usually closed within the first 6 to 8 weeks after birth, with many closing between 1 to 3 months of age.
The anterior fontanelle, the larger soft spot on top of the head, takes considerably longer to close. While there is a range of normal closure times, it generally closes between 7 and 19 months of age, with an average around 12 to 14 months. In some cases, it may remain open until 24 months or even up to 26 months. Pediatricians routinely monitor fontanelle size and closure during well-baby check-ups as part of assessing overall development. While variations within these ranges are common, premature closure (before 6 months for the anterior fontanelle) or significantly delayed closure can sometimes indicate underlying medical conditions and should be discussed with a healthcare provider.