Microcephalus (also called microcephaly)


Condition Description

Microcephaly (my-kro-SEF-ah-lee) means small (micro) head (cephaly). It is a rare neurological condition in which the infant’s head is smaller than normal compared to other infants of the same age and sex. The condition can be present at birth or develop within the first few years of life.

Microcephalus (my-kro-SEF-ah-lus) is of two types. Primary microcephalus occurs with no identifiable cause as an inherited trait in families where many members are born with small head sizes. Secondary microcephalus occurs when the brain's growth is decreased because of conditions that can be identified: chromosomal anomaly such as Down syndrome, congenital infections with organisms such as the virus rubella, metabolic disorders, bacterial meningitis, or lack of oxygen early in life (called hypoxic-ischemic encephalopathy). A mother who uses drugs or alcohol during pregnancy can also have a child with microcephalus. Exposure to radiation or chemicals can also produce a small head size (and thus, small brain). The number of children with primary microcephalus is 1 in 40,000 live births, making this a rare condition. The prevalence of secondary microcephalus much higher, but it is hard to estimate since it results from multiple conditions. Our program has been tracking microcephalus among live births in select counties since 2005 and gradually are expanding statewide.

  • Using data from births to Hennepin and Ramsey county residents between 2007-2011, we found that 5.9 babies were born with microcephalus per 10,000 births.
  • Using this data, we estimate about 42 babies are born with microcephalus every year in Minnesota.

Parental education and support are essential, and local, regional and national organizations may be very helpful.

Condition specific organizations

Additional information and resources for families are available.