Symptoms

The primary sign of microcephaly is:

• A head size significantly smaller than that of other children of the same age and sex

Head size is measured as the distance around the top of the child's head (circumference). Using standardized growth charts, the measurement is compared with other children's measurements in percentiles.

Some children just have small heads, whose measurement falls as low as the first percentile. In children with microcephaly, head size measures significantly below average, possibly even below the first percentile for your baby's age and sex.

A child with more severe microcephaly may also have a backward-sloping forehead.

When to see a doctor

Chances are your doctor will detect microcephaly at the baby's birth or at a regular well-baby checkup. However, if you think your baby's head is smaller than normal or isn't growing as it should, talk to your doctor.