How is a diagnosis of microcephaly made?

A diagnosis of microcephaly is made based on the measurement of the head circumference. The head circumference is measured around the largest part of the head, just above the eyebrows and over the ears. It is important to note that head size can vary based on ethnicity and other factors, so a diagnosis of microcephaly is made when the head circumference is significantly smaller than what is expected for the child's age and sex.

In addition to the head circumference measurement, a doctor will also consider other factors such as:

- The shape of the head

- The child's overall growth and development

- The presence of other medical conditions

Imaging studies, such as a CT scan or MRI, may also be done to evaluate the brain and rule out other possible causes of the small head size.