Published: February 14, 2022
Ian S. Mutchnick, M.D. is a pediatric neurosurgeon with Norton Children’s Neuroscience Institute, affiliated with the UofL School of Medicine.
Babies’ brains grow very quickly. Therefore, the bones of a baby’s skull are not connected to each other, which allows the skull to expand easily to keep up with the growth.
In two “soft spots” – one on top of the head (the anterior fontanelle) and one on the back of the head (the posterior fontanelle) – the spaces between the bones are particularly wide, leaving the brain underneath more vulnerable to injury. Luckily, we almost never see damage to the brain through the fontanelles, because we are so gentle with babies!
The soft spot on the back of the head closes by age 3 months. The larger soft spot in front can close as early as 4 months and as late as 24 months; most are closed by 18 months. Because there is no bone over the brain, these soft spots can allow us to see brain problems.
Even though it is soft, the fontanelles still provide good brain protection for the baby. If a baby accidentally bumps their soft spot during play or normal baby activities, I would not worry about it too much, unless you can see bruising, a cut or other kinds of damage to the skin.
A baby’s soft spot can be bowed slightly inward or upward, but as long as it is soft, things are probably OK. If you notice that the soft spot pulsates sometimes, don’t be alarmed. This is a result of the baby’s blood pulsing with their heartbeat.
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Be gentle while touching your baby’s head. Soft spots are covered by a thick, fibrous layer of tissue. So while it is safe to touch them, they should not be handled roughly or allowed to be struck forcefully.
A dramatically sunken fontanelle or a persistently bulging fontanelle, accompanied with poor feeding, vomiting, drowsiness or failure to thrive are issues to raise with your pediatrician.
Soft spots serve an important purpose during childbirth: allowing the baby’s head to be moldable during a vaginal delivery.