What do you know about infant fontanelle?

If you run your fingers gently over an infant's head, you may feel some soft, bony depressions instead of hard bones. These are soft spots where your baby's skull bones don't fuse together. Called fontanel. The fontanelle is considered part of a baby's development. However, changes in the fontanelle can sometimes be a sign of a serious health problem. You can gently touch or bathe your baby's fontanel without worrying. They are covered by a thick and sturdy membrane that helps them to well protect the brain inside during daily activities.


1. What is fontanelle?

At birth, a newborn's skull consists of five major bones:

  • 2 frontal bones.
  • 2 parietal bones.
  • 1 occipital bone.

The upper bones are separated by connective tissue fibers known as cranial sutures. These lines function as seams. They are essential to facilitate movement of the skull, even overlap, as the baby passes through the mother's pelvis during labor. The craniofacial line also helps to accommodate the rapid postnatal growth and development of the brain. However, unlike adults, infants have skull bones that are not tightly linked together. Thus, the fontanelle structure is formed. This is one of the most prominent features of the skull in infants.

2. When does the fontanel close?

You can feel a fontanelle in the front on the top of the head and one in the back of the head. The fontanel shape can vary between babies. But the feature is that they are flat and soft. Over time, the bones grow larger and the fontanelle closes. The fontanelle at the back of a baby's head usually closes by the time he's 2 months old. The anterior fontanel usually closes between the ages of 7 months and 18 months. A newborn baby's brain begins to grow amazingly. In the first 9 months, it will double in size. And by 36 months, it will have tripled in size.

3. The structure of the fontanels

3.1 Anterior fontanel

3.1.1 General characteristics

The anterior fontanel is the largest of the six fontanels. It is like a diamond measuring from 0.6 cm to 3.6 cm. The fontanelle is formed by the juxtaposition of the two frontal and two parietal bones. Between these bones are connected by cranial joints.

The average time for the anterior fontanelle to close is between 13 and 24 months. In terms of gender, the anterior fontanelle size of male infants is smaller than that of female infants. The most common conditions that cause anterior fontanelle enlargement or late closure include: Down syndrome, osteochondrosis, congenital hypothyroidism , rickets, and conditions that increase brain size. 

3.1.2 Pathological characteristics

In addition to having the largest size, the anterior fontanelle is also considered the most important for diagnosis. This structure provides insight into the infant's health status. Especially dehydration and increased pressure on the skull. 

Anterior fontanel depression is mainly due to dehydration. Children may vomit or have diarrhea many times. Other signs that suggest a diagnosis of dehydration are dry lips, sunken eyes, and crying without tears. In addition, the presence of a bulging fontanelle may suggest a variety of conditions: hydrocephalus, intracerebral hemorrhage, meningitis, or trauma.

Less common causes may be: Vitreous bone disease, bone malformations due to hypophosphatemia, Patau syndrome (Trisomy 13), Down syndrome (Trisomy 18), congenital rubella infection , syphilis, Drug-induced malformations, malnutrition, intrauterine growth retardation. 

Down syndrome is a genetic disorder that affects the development of the brain and other organs. Children with Down syndrome develop poorly both physically and mentally. Children often learn more slowly, think and solve problems more slowly than their peers.

2.2 Posterior fontanel

Unlike the anterior fontanelle, the posterior fontanelle is triangular in shape and completely closes between 6 and 8 weeks after birth. This structure arises from the fusion of the parietal and occipital bones. On average, the posterior fontanelle size is 0.5 - 0.7 cm in neonates. Usually, late posterior fontanelle closure is associated with hydrocephalus or congenital hypothyroidism.

What do you know about infant fontanelle?

Quadrilateral anterior fontanelle and triangular posterior fontanel

2.3 fontanelle in mastoid

This is a paired structure, which can be found at the intersection of the temporal, parietal, and occipital bones. It is also referred to as the posterior lateral fontanelle. These fonts can close anytime between 6 and 18 months of age.

2.4 fontanelle in the sphenoid bone

Similarly, the fontanelle in the sphenoid bone is made up of many different bony structures. Its location is possible on either side of the skull with attachments of the sphenoid, parietal, temporal, and frontal bones. It is also known as anterior anterolateral fontanelle. The time of fontanel closure occurs around the 6th month after birth.

2.5 Third fontanelle

It is unique in the presence of a third fontanelle between the anterior and posterior fontanelles in children with Down syndrome and congenital infections such as rubella. The reported frequency of this third fontanelle was 6.4% among 1020 randomized neonates.

What do you know about infant fontanelle?

The process of fontanel closure in the neonate

3. Does abnormal fontanel need surgical treatment?

Depending on the specific pathology affecting the anterior fontanel, surgical intervention may be necessary. For example, if an infant is diagnosed with an ankylosing spondylitis early in childhood, there will be an increase in pressure in the skull. The consequences can lead to serious brain damage or even death. Surgical intervention for any pathology depends on the assessment of the Doctor on a case-by-case basis.

4. What problems do you need to pay attention to related to the fontanelle of the child?

Like any medical visit, the Doctor will collect a detailed history and perform a thorough physical exam of your child. From there, determine the diagnosis and give the appropriate treatment. As a parent, you need to keep the following points in mind:

  • The process of pregnancy and birth of a newborn baby is favorable or not. Intrauterine growth retardation or malnutrition is also a notable factor. Natural birth methods are easy or require the help of equipment. Are there any complications of birth such as stacking of skull bones or serous tumors of the head?

What do you know about infant fontanelle?

Monitor baby's head circumference

  • Observe and feel your child's skull as well and monitor each day. It is also important to monitor the increase or decrease in head circumference or change in the shape of the fontanelle. In addition, you may feel the fontanel bulging or deepening. Accurate results occur when the infant is at his most comfortable, possibly sleeping. Because the fontanelle can swell when a child is angry or fussy. Then return to normal as the baby gradually settles down.
  • If the bulge doesn't return to normal, it could be a sign of a serious condition. Especially meningitis. Take the child to the doctor immediately in this case. Especially if the baby has a fever or is lethargic, stop feeding.

What do you know about infant fontanelle?

You don't need to worry when touching the fontanel

It can be a tough time to start parenting. With so much to learn about taking care of your baby. Of the things you have to learn, the dimple on your baby's head (called the fontanelle) can cause you even more anxiety. The good news is that these soft spots are simple to care for and usually disappear by the time your child is 2 years old. Some parents may feel nervous about fontanelle touching. However, there is no need to be too scared or avoid touching your baby's fontanelles. Because they are protected by a hard layer of tissue.

Newborn fontanelle is a rather sensitive part of children. It reflects the physiological as well as pathological conditions of the child. Understanding the characteristics of fontanelles in children helps parents know when to take their child to the doctor.