Diagnosis

To determine whether your child has microcephaly, your doctor likely will take a thorough prenatal, birth and family history and do a physical exam. He or she will measure the circumference of your child's head, compare it with a growth chart, and remeasure and plot the growth at future visits. Parents' head sizes also may be measured to determine whether small heads run in the family.

In some cases, particularly if your child's development is delayed, your doctor may request tests such as a head CT scan or MRI and blood tests to help determine the underlying cause of the delay.