Microcephaly (Mi-cro-CEF-alee) is usually a birth defect. It occurs when a baby is born with a head much smaller than normal. Microcephaly can result in intellectual and developmental disabilities ranging from mild to severe.

Zoe's Story

At the beginning of the third trimester, Zoe had an ultrasound *

What Is Microcephaly?

A child with microcephaly has an unusually small head for its age and sex. The condition usually is a birth defect, although it can also be caused by traumatic brain injury, lack of oxygen reaching the brain, or a brain infection early in childhood. Microcephaly can occur alone or in combination with other birth defects.

Some children with microcephaly develop normally and have normal intelligence. In others, the condition results in mild to severe learning disabilities, problems with movement and balance, problems with fine motor skills, speech delays, seizures, and abnormal facial features. Sometimes the condition is associated with reduced height or dwarfism * . Although microcephaly is often apparent at birth, the degree and type of disabilities usually do not become apparent until the child begins to grow and develop.

Microcephaly has several causes or the cause may be unknown. Possible causes include:

How Common Is Microcephaly?

Is Microcephaly Contagious?

Microcephaly itself is not contagious. However, the viruses that can cause microcephaly are contagious. Care should be taken to avoid viral infection during pregnancy. Women who have not had German measles (rubella) or chickenpox and who plan to become pregnant can be vaccinated against these diseases if they receive the vaccine several months before attempting to become pregnant. Pregnant women should avoid cat feces and should not clean cat litter boxes. If cleaning a litter box is unavoidable, they should wear gloves and wash their hands well afterward.

The Zika virus presents special problems for pregnant women. It is transmitted by a mosquito that lives in warm, humid climates and bites during both the day and night. Eighty percent of people who are infected have no symptoms, and the remaining 20 percent have only mild symptoms. Many people do not realize they have contracted the virus. The virus remains in the semen of infected men for at least two weeks and can be transferred to women through sexual intercourse. Condom use can help prevent transmission of the virus.

How Do Doctors Diagnose and Treat Microcephaly?


Microcephaly is most often physically obvious at birth or during infancy, although many of the effects of the disorder become obvious only later during childhood. Children with severe microcephaly often have very small heads with a forehead that slopes noticeably backward and may have feeding problems as a newborn.

Sometimes microcephaly is diagnosed during a routine ultrasound at the end of the second trimester or during the third trimester of pregnancy. When it is not diagnosed before birth, it is diagnosed when the baby is born by measuring the circumference of the head and charting changes in head size over time.


Microcephaly is a lifelong disorder for which there is no cure. Nevertheless, some children show little impairment and lead normal lives. In rare cases, microcephaly caused by early fusion of the bones of the skull may be treated with surgery to give the brain room to grow.

Although there is no cure for microcephaly, children with the condition benefit from early interventions that address their specific disabilities. This may involve physical, occupational, and/or speech therapy. Older children may benefit from psychological counseling, as may parents and siblings who must adjust to living with a child with disabilities.

Can Microcephaly Be Prevented?

See also AIDS and HIV Infection • Birth Defects: Overview • Chickenpox (Varicella) • Cytomegalovirus (CMV) Infection • Down Syndrome • German Measles (Rubella) • Phenylketonuria • Syphilis • Toxoplasmosis • Zika Virus Infection


Books and Articles

Brasil, Patricia, et al. “Zika Virus Infection in Pregnant Women in Rio de Janeiro—Preliminary Report.” New England Journal of Medicine, E pub, March 4, 2016. http://www.nejm.org/doi/full/10.1056/NEJMoa1602412 (accessed March 13, 2016).


Boston Children's Hospital. “Microcephaly in Children.” http://www.childrenshospital.org/conditions-and-treatments/conditions/microcephaly (accessed March 13, 2016).

Centers for Disease Control and Prevention. “Facts about Microcephaly.” http://www.cdc.gov/ncbddd/birthdefects/microcephaly.html (accessed March 13, 2016).

World Health Organization. “Microcephaly.” http://www.who.int/mediacentre/factsheets/microcephaly/en (accessed March 13, 2016).


March of Dimes Foundation. 1275 Mamaroneck Ave., White Plains, NY 10605. Telephone: 914-997-4488. Website: http://www.marchofdimes.com (accessed March 13, 2016).

* ultrasound is a diagnostic test in which sound waves passing through the body create images on a computer screen. Also called a sonogram.

* dwarfism is a congenital disease of bone growth that results in short stature and weak bones.

* Zika (zee-ka) virus is a microbe transmitted to humans by mosquitoes. Although most people have mild or no symptoms, Zika infection of a pregnant woman can cause serious birth defects in the fetus.

Disclaimer:   This information is not a tool for self-diagnosis or a substitute for professional care.

(MLA 8th Edition)