Dehydration is the primary cause of a sunken fontanel. Dehydration occurs when an infant does not have sufficient fluid in their body to maintain normal functioning.

When should I worry about a sunken fontanelle?

Sometimes it can bulge slightly (such as when baby cries), and less often, it can appear to be concave, or sunken. It's okay if it curves inward slightly to the touch. But if the soft spot is significantly sunken, it's usually a sign that your baby is dehydrated and needs to be given fluids immediately.

What does a sunken fontanelle indicate?

The fontanelles should feel firm and very slightly concave to the touch. A noticeably sunken fontanelle is a sign that the infant does not have enough fluid in its body. The sutures or anatomical lines where the bony plates of the skull join together can be easily felt in the newborn infant.