As a rule of thumb, a newborn's head is usually about 2 centimeters larger than the chest size. Between 6 months and 2 years, both measurements are about equal. After 2 years, the chest size becomes larger than the head.

A series of measurements over time that show an increased rate of head growth often can provide more valuable information than a single measurement that is larger than expected.

Increased intracranial pressure (increased pressure within the head) often accompanies increased head circumference. Symptoms associated with this condition�include vomiting, eyes deviating downward, and irritability.

See also bulging fontanelles.

• Hydrocephalus (congenital, post-traumatic, or obstructive)
• Canavan disease
• Hurler syndrome
• Morquio syndrome
• Benign familial macrocephaly (family tendency toward large head size)
• Intracranial bleeding

Macrocephaly is usually discovered by the health care provider during a routine well-baby exam.

The medical history will be obtained and a physical examination performed.

Medical history questions documenting increased head circumference in detail may include:

• Time pattern
  • When did you first notice that the baby's head seemed large?
  • Does the baby's head size seem to be increasing faster in proportion to the growth of the body?
• Location
  • Does the head seem larger all over?
  • Is the head growing more in a front-to-back pattern or in a side-to-side pattern?
• Other
  • What other symptoms are also present (especially changes in brain or nervous system functions)?

Physical examination may include repeated measurements of the�head circumference�over a period of time to confirm that the head circumference is significantly increased. In some cases a single measurement is sufficient to confirm a significant increase.

Diagnostic tests may vary depending on the suspected cause, but often include:

• MRI of the head
• Head CT scan

After seeing your health care provider:

If a diagnosis was made by your health care provider of the cause of increased head circumference, you may want to note that diagnosis in your personal medical record. You may also want to document your own measurements of the head circumference.