Fontanelles Explained: Your Baby's Soft Spots

Have you noticed a soft, slightly sunken area on your baby’s head? Is this normal? Should I be concerned? 

As a Certified Sleep Sense Consultant at Lullabub Sleepers, I’ve had countless conversations with parents in Singapore who are concerned about fontanelles—also known as “soft spots”—on their baby’s head. The good news? These soft spots are completely normal and play a crucial role in your baby’s growth and development. 

Let’s break down what fontanelles are, why they exist, and how to care for them, while also discussing how they relate to sleep training a baby.  

What Are Fontanelles? 

Fontanelles are soft spots on a baby’s skull that allow for brain growth and easier passage through the birth canal. Unlike adult skulls, which are made of fused bones, newborns have gaps between their skull bones that gradually close as they grow.

There are six fontanelles, but the most noticeable ones are: 

✔ Anterior Fontanelle (Top of the Head) – The largest and most felt soft spot. 

✔ Posterior Fontanelle (Back of the Head) – Much smaller and closes earlier. 

These soft spots are covered by a thick protective membrane, so while they may look delicate, they are not as fragile as they seem. 

When Do Fontanelles Close? 

Fontanelles close gradually as your baby’s skull bones fuse together: 

🍼 Posterior Fontanelle – Closes by 2 to 3 months old 

🍼 Anterior Fontanelle – Closes between 12 to 18 months old 

If your baby's soft spot is still open after 2 years, consult a pediatrician to rule out any underlying issues.  

How Fontanelles Affect Sleep Training a Baby 

Many parents worry that sleep training a baby could put pressure on fontanelles or cause harm. Rest assured, it won’t. 

💤 Normal sleep positions (back sleeping) are safe and won’t damage fontanelles. 

💤 Gentle sleep training methods, such as gradual fading or pick-up-put-down, are ideal for newborns as they adjust to independent sleep. 

💤 Avoid excessive pressure on the same spot by alternating head positions during naps. 

Ensuring your baby gets quality sleep is key to brain growth and healthy skull development—another reason why sleep training is beneficial. 

Common Concerns About Fontanelles 

1. Why Is My Baby’s Fontanelle Pulsating? 

It’s completely normal! The fontanelle is close to blood vessels, so you may see a slight pulse when your baby is crying or feeding. 

2. What If the Soft Spot Seems Sunken? 

A sunken fontanelle may indicate dehydration, especially if your baby is also lethargic or not producing enough wet diapers. Offer more feeds and seek medical attention if it persists. 

3. What If the Fontanelle Is Bulging? 

A bulging soft spot, especially with fever or vomiting, may signal infection or fluid buildup. Contact your doctor immediately. 

How to Care for Your Baby’s Fontanelles 

Taking care of fontanelles is easy and doesn’t require special treatment. Here’s what to keep in mind: 

✔ Be Gentle, But Don’t Be Afraid to Touch It – The soft spots are well protected, so normal washing and brushing won’t harm them. 

✔ Avoid Excessive Pressure – Encourage tummy time to prevent your baby from resting their head in one position for too long. 

✔ Monitor for Changes – Keep an eye on any unusual bulging or sunken areas. 

✔ Follow a Healthy Sleep Routine – Good sleep supports brain growth, which is essential for skull development. 

Lullabub Sleepers – Helping Parents Through Every Stage 

Whether it’s understanding newborn development, managing sleep regressions, or creating a sleep routine that works, Lullabub Sleepers is here to help. 

If you’re struggling with sleep training a baby and need expert guidance, check out my coaching enquiry designed for babies in Singapore. 

Learn more about my sleep support services here. 

Final Thoughts: Fontanelles Are a Sign of Growth 

Your baby’s soft spots are a natural part of development, and as they grow, these fontanelles will close at the right time. In the meantime, focus on ensuring your baby gets the sleep they need to support healthy growth and development. 

If you’re concerned about your baby’s sleep habits, I’m here to help. Together, we can create a gentle, effective sleep plan that works for your little one. 

FAQs 

At what month does the fontanelle close? 

The posterior fontanelle (back of the head) typically closes by 2 to 3 months, while the anterior fontanelle (top of the head) closes between 12 to 18 months. In some cases, it may take up to 24 months for full closure.  

What is the circumference of a newborn's head in Singapore?

The average head circumference for newborns in Singapore is about 33 to 35 cm at birth. This measurement varies slightly based on genetics, birth weight, and overall growth.

What are the 6 fontanelles of a newborn?

A newborn has six fontanelles: 

• Anterior Fontanelle – Located at the top of the head (the largest and most noticeable). 

• Posterior Fontanelle – Located at the back of the head (smaller and closes earlier). 

• Right Sphenoid Fontanelle – Located near the right temple. 

• Left Sphenoid Fontanelle – Located near the left temple. 

• Right Mastoid Fontanelle – Located behind the right ear. 

• Left Mastoid Fontanelle – Located behind the left ear. 

The anterior and posterior fontanelles are the ones parents usually notice, but the sphenoid and mastoid fontanelles also play a role in skull flexibility and development. 

What is the jaundice level for infants in Singapore?

In Singapore, mild jaundice is common and monitored using bilirubin levels. Doctors may treat levels above 250 µmol/L in full-term babies, while preterm babies may require intervention at lower levels. 

What if my 2-year-old's fontanelle is not closed?

If the anterior fontanelle hasn’t closed by 24 months, consult a pediatrician. Delayed closure may indicate conditions like hypothyroidism, rickets, or hydrocephalus, though some babies just take longer to reach this milestone. 

What if I accidentally hit my baby's soft spot?

Fontanelles are covered by a tough membrane that protects the brain. A gentle bump is unlikely to cause harm, but if your baby shows vomiting, extreme fussiness, or loss of consciousness, seek medical attention immediately.

When to worry about a baby’s soft spot?

Contact a doctor if the fontanelle is bulging (a sign of increased pressure), sunken (a sign of dehydration), or remains open beyond 24 months. Any swelling, redness, or abnormal shape should also be checked. 

What causes delayed closure of the fontanel?

Factors like genetic variations, hypothyroidism, rickets (vitamin D deficiency), hydrocephalus, or certain syndromes can delay fontanelle closure. A pediatrician can assess growth patterns and run tests if needed. 

How to tell if a fontanelle is sunken?

A sunken fontanelle appears slightly depressed compared to the surrounding skull. It may also be accompanied by dry skin, fewer wet diapers, fussiness, or lethargy, which are signs of dehydration. 

What happens if a baby’s soft spot closes too soon?

Premature closure of the fontanelle, known as craniosynostosis, can affect skull growth and brain development. If noticed early, treatment may include helmet therapy or surgery to correct skull shape.

How big should the fontanelle be at 6 months?

By 6 months, the anterior fontanelle typically measures 1 to 3 cm in diameter. The size gradually decreases as the skull bones fuse together. 

When to worry about a baby’s head shape?

If your baby’s head appears uneven, flattened on one side, or has unusual ridges, consult a doctor. Plagiocephaly (flat head syndrome) is common but treatable with repositioning, tummy time, or in severe cases, helmet therapy.