Why isn't my two-month-old baby's fontanel 'breathing'?

My baby was born in mid-July, and currently the fontanelle on the top of his head isn't pulsating as he breathes. Why is this happening, and is this dangerous? (Ha My, An Giang )

Reply:

Humans breathe and exchange oxygen in their lungs. The fontanelle is completely uninvolved in respiratory activity; therefore, the common term "breathing fontanelle" is incorrect. In some newborns, parents may notice the fontanelle pulsating when crying or straining, because the area of the brain containing the fontanelle has not yet been completely closed by the bone, a condition known as an open fontanelle.

At birth, a baby's head has two fontanelles: the anterior and posterior, which are easily felt as soft spots during bathing, shampooing, or when putting on a hat. The anterior fontanelle is quadrilateral in shape, measuring 2.5 x 2.5 cm, and is covered by a fibrous membrane. It usually closes by 18 months of age. However, more than 27% of babies have their anterior fontanelle closed by 12 months.

The posterior fontanelle is a triangular structure bounded by the parietal and occipital bones (bones that do not completely cover the skull). Normally, after birth, this fontanelle is very small, only about the size of a baby's fingernail, difficult to detect, and closes after 2-3 months of age.

If the fontanelle closes early but the child's head circumference is still within the standard range and development is normal, there is no cause for concern. However, children with early fontanelle closure need to be monitored. If the child's head circumference changes from the standard, a doctor needs to conduct a more in-depth examination to find the cause. If the fontanelle closes early and the head circumference is small for the child's age, the child may have microcephaly.

If the fontanelle is dilated and closes late, the child may have rickets, hydrocephalus, increased intracranial pressure, hypothyroidism, etc. If the fontanelle is sunken, beware of dehydration, malnutrition, and growth retardation.

Infants with bulging fontanelles should be aware of certain medical conditions, such as meningoencephalitis, cerebral hemorrhage, hydrocephalus, or the use of certain medications, and should be taken to the doctor immediately.

Dr. Pham Le My Hanh
Head of the Neonatology Department, Neonatal Center, Tam Anh General Hospital, Ho Chi Minh City

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