Fontanelles

People usually notice only the one at the top of a baby’s head, but there are six fontanelles present in every newborn, one each of the posterior and anterior, and two each of sphenoid and mastoid fontanelles:

• Posterior fontanelle: The soft space at the back of your baby’s head is called the posterior fontanelle. This triangular shaped, half-inch wide fontanelle often goes unnoticed, and closes up the first.
• Anterior fontanelle: The Anterior fontanelle is the soft opening on the top of your baby’s head, and is the most noticeable one as it is the largest. It’s roughly about an inch in size, but can be bigger or smaller depending on the individual baby. As it is the largest of the fontanelles, this one also takes the longest to close.
• Sphenoid fontanelle: These fontanelles are present on either side of the temple of the skull towards the front.
• Mastoid fontanelle: Also two in number, the mastoid fontanelles are soft spots on each side of the head, behind the ears of the baby.

After birth, the soft spots remain open as the baby’s brain still needs space to grow. The opening between the skull bones close once the brain grows and assumes its final shape and size. However, they don’t close together, as each one takes its own time:

• The posterior fontanelle is the first to close up inside the first three months.
• The Anterior fontanelle remains open for the longest duration, and closes up well past the child’s first birthday, and takes between 18 months and two years of age to close.
• It takes about six months for the sphenoid fontanelle to close.
• The ones behind each ear - Mastoid fontanelle - take between six to 18 months to close.

As they are quite good indicators of the health and development of a baby, doctors will frequently check the soft spots and make their observations based on their findings. Typically, however, the fontanelles should look even from a distance and only soft to the touch.

Sunken or bulging fontanelles, however, must be reported to the doctor as they could provide clues for underlying concerns.

Although normal for fontanelles to have a slight internal curve, a sunken fontanelle is a sign of dehydration. Lack of fluids is the most significant reason behind dehydration. Check for the following symptoms for dehydration if you notice a sunken fontanelle:

• Fever
• Vomiting
• Loose motions
• Lack of interest in his feeds
• Dry mouth
• Passing less urine
• Unusual sleepiness

A bulging fontanelle is normal when a baby is crying or pooping, as it replicates the pulse of the baby. It will settle down to its normal position once the baby calms down. However, a state of continuous bulge or swollen fontanelle is a sign of swelling or inflammation in the brain, or underlying illnesses like meningitis, head trauma or building up of fluid, and requires immediate attention.

Fontanelles that are larger than their usual size and take longer to close can be a sign of serious health problems like Down syndrome, rickets and Hypothyroidism. Consult your doctor if you observe any of the above conditions.