When a baby’s soft spot appears sunken, it can be a source of concern for parents. This area on a baby’s head, known as a fontanelle, is a normal part of their development. Understanding what a soft spot is and why it might look sunken can help parents respond appropriately.
What is a Baby’s Soft Spot?
A baby’s soft spots, medically termed fontanelles, are spaces between the bones of the skull that have not yet fused together. Babies are typically born with two main fontanelles: the larger anterior fontanelle, located on the top-front of the head, and a smaller posterior fontanelle at the back. These areas are covered by a tough, fibrous membrane that protects the brain, making them less fragile than they might seem.
The presence of fontanelles serves two important purposes. They allow the skull bones to compress and overlap, aiding the baby’s passage through the narrow birth canal during delivery. Additionally, these soft spots accommodate the rapid growth of a baby’s brain during the first year of life. A normal fontanelle should feel relatively flat or slightly depressed and may even show a visible pulsation, which is the blood flowing with the heartbeat. The posterior fontanelle usually closes by about 2 to 3 months of age, while the larger anterior fontanelle typically closes between 9 and 18 months, though it can remain open until 24 months.
Common Reasons for a Sunken Soft Spot
A primary reason a baby’s soft spot might appear sunken is dehydration, which occurs when an infant does not have enough fluid in their body. This can happen if a baby is not taking in enough fluids, or if they are losing fluids rapidly through vomiting, diarrhea, or a fever. When the body loses fluids, including the cerebrospinal fluid that surrounds the brain, the fontanelle can appear more depressed.
Beyond a sunken fontanelle, other indicators of dehydration in infants include a decrease in wet diapers, with fewer than six wet diapers per day being a sign for infants. The baby might also have a dry mouth or lips, appear unusually sleepy or less alert, and produce few or no tears when crying. Their eyes might also look sunken. While dehydration is the most frequent cause, in less common instances, a sunken fontanelle can also be associated with malnutrition.
When to Consult a Doctor
Prompt medical attention is warranted if a baby’s soft spot appears significantly sunken, particularly when combined with symptoms like severe lethargy, an inability to keep fluids down, persistent high fever, a significant reduction in urination, or unusually dark urine.
Contact a healthcare provider if a baby seems unusually drowsy, irritable, has consistently sunken eyes, or shows any notable change in the fontanelle’s normal appearance, especially if not acting well or experiencing vomiting or diarrhea.