The measurement and evaluation of the head circumference represent, together with other anthropometric parameters (length, weight, thickness of the triceps folds, abdominal and thoracic circumference), an excellent indicator for evaluating the growth of the infant and child.
How it is measured
The head circumference can also be measured during intrauterine life, through echocardiographic examinations and always with the aim of evaluating the correct development of the fetus. In this case, however, it is preferred to relate it to the abdominal one.
Normal values
Very often the circumference of the skull is related to that of the chest; at the moment of birth the skull prevails, within the year the two measures are equivalent and above this age the chest is larger than the head. After birth, in fact, the head circumference grows rapidly (approx. 11 cm in the first 12 months) , after which it increases by only 4 centimeters over the next 9. The chest circumference, on the other hand, increases in a slower but constant way.
75 cm (males)
74 cm (females)
88 cm (males)
86 cm (females)
10.55 kg (male)
10.00 kg (females)
13.05 kg (males)
12.50 kg (females)
35 cm (males)
35 cm (females)
47 cm (males)
46 cm (females)
49 cm (males)
48 cm (females)
In the adult, the head circumference reaches on average:
- 58 cm in the male (± 3 cm depending on whether the subject is ± tall)
- 55 cm in the female (± 3 cm depending on whether the subject is ± tall)
Anomalies of the head circumference
Macrocephaly
The head circumference can border on excess abnormality (macrocephaly) due to a disease known as hydrocephalus (increased cerebral spinal fluid contained in the cerebral ventricles and subarachnoid spaces). Hydrocephalus recognizes several causes and, when not treated in time , causes psychomotor retardation, spasticity and seizures. Macrocephaly can also be the consequence of Paget's disease, a chronic degenerative bone disease.
Microcephaly
Pathological values below the norm (microcephaly) are an indication of brain malformations and mental insufficiency. Also in this case the causes can be different (alcoholism, smoking, syphilis, hormonal alterations - especially thyroid - and metabolic).
We remind you that alcohol abuse during pregnancy exerts a heavy teratogenic action and, as such, interferes with the normal development of the fetus, causing damage to various organs and functions (fetal alcohol syndrome). Among these, there is also the possibility that the head circumference is less than normal, resulting in an anomaly in mental development.
Growth percentages
To establish the adequacy of the head circumference, it is necessary to compare it with that of other subjects of the same age and sex. To do this, it is necessary to have specific tables and graphs, which show the values found in the rest of the population.
The growth curves, freely available at the end of the article, are widely used for this purpose (although referring to the US population, they are also very indicative for the European population).
Even if to an inexperienced eye they can be difficult to interpret, just remember that each curve designates a percentile, that is, the percentage of the population that has a value lower or higher than the standard. For example, a child with a head circumference corresponding to the 75th percentile has 75% of peers with lower values and 25% with higher values.
On the basis of these data, head circumferences between the 3rd and 97th percentile are considered in the norm, even if anomalous values do not always have a pathological significance.
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