A fontanelle, commonly known as a soft spot, is a space between the bones of an infant’s skull where the sutures intersect. Babies are born with several fontanelles, covered by tough membranes that protect the underlying soft tissues and brain. The two most prominent are the anterior fontanelle, on top of the head, and the posterior fontanelle, at the back of the head.
These gaps serve two main purposes. First, they allow the skull’s bony plates to flex and overlap during childbirth, enabling the baby’s head to pass through the birth canal. Second, fontanelles accommodate the rapid growth of the brain during the first year of life, as the brain expands faster than the surrounding bone. The posterior fontanelle closes within the first few months of life, while the larger anterior fontanelle closes between 7 and 19 months of age.
Understanding a Sunken Fontanelle
A sunken fontanelle appears as a noticeable dip or concavity in the soft spot on a baby’s head, looking as though it has caved inward. Normally, a baby’s fontanelle should appear flat and feel firm to the touch.
While a slightly depressed fontanelle can be normal, a significantly sunken fontanelle warrants attention. This inward curvature indicates the baby’s body may not have enough fluid. A well-hydrated baby will have a fontanelle that remains flat and firm.
Primary Causes and Accompanying Symptoms
Dehydration is the most common cause of a sunken fontanelle in infants. This occurs when a baby loses more fluid than they consume, due to reasons such as vomiting, diarrhea, fever, or not drinking enough fluids.
Dehydration often accompanies a sunken fontanelle with several other noticeable symptoms. Parents may observe fewer wet diapers, indicating decreased urine output. The baby’s mouth and lips might appear dry, and they may produce few or no tears when crying.
Additional signs of dehydration include lethargy, increased irritability, and unusually dry or cool skin. In more severe cases, a baby might exhibit a rapid heart rate or breathing, and their eyes may appear sunken.
When to Seek Medical Care and Prevention
Immediate medical attention is necessary if a baby displays a significantly sunken fontanelle along with other signs of severe dehydration. These signs include persistent vomiting or diarrhea, a high fever, extreme lethargy, or if the baby is unusually drowsy or irritable. A healthcare provider should assess the severity of dehydration and determine the appropriate course of action.
Preventing dehydration involves ensuring adequate fluid intake. Parents should offer more frequent feedings, whether breastfeeding or bottle-feeding, especially during periods of illness like fever, vomiting, or diarrhea. If the baby is on formula or solid foods, small sips of extra water can be offered.
Avoiding overheating is also a preventative measure, as excessive sweating can contribute to fluid loss. Promptly increasing fluid intake as soon as a baby experiences vomiting or diarrhea can help prevent the fontanelle from becoming sunken. Consulting a pediatrician with any concerns about feeding or potential dehydration is advisable.