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Microcephaly is a medical condition in which the circumference of the head is small because the brain has not fully developed or has stopped growing. Microcephaly can be present at birth or it may develop in the first few years of life. It is most often caused by genetic abnormalities that interfere with the growth of the cerebral cortex during the early months of fetal development. Babies may also be born with microcephaly if, during pregnancy, their mother:

  • Abused drugs or alcohol
  • Became infected with a cytomegalovirus, rubella (German measles), varicella (chicken pox) virus, or possibly zika virus
  • Was exposed to certain toxic chemicals
  • Had untreated phenylketonuria (PKU), a harmful buildup of the amino acid phenylalanine in the blood

Microcephaly is associated with Down's syndrome, chromosomal syndromes, and neurometabolic syndromes. With viral-induced brain injury there is often widespread tissue and cell death leading to brain shrinkage rather than simply impaired growth.

Depending on the severity of the accompanying syndrome, children with microcephaly may have:

  • Impaired cognitive development
  • Delayed motor functions and speech
  • Facial distortions
  • Dwarfism or short stature
  • Hyperactivity
  • Seizures
  • Difficulties with coordination and balance
  • Other brain or neurological abnormalities

How can I or my loved one help improve care for people with microcephaly?

Consider participating in a clinical trial so clinicians and scientists can learn more about microcephaly and related disorders. Clinical research uses human volunteers to help researchers learn more about a disorder and perhaps find better ways to safely detect, treat, or prevent disease.

All types of volunteers are needed—those who are healthy or may have an illness or disease—of all different ages, sexes, races, and ethnicities to ensure that study results apply to as many people as possible, and that treatments will be safe and effective for everyone who will use them.

For information about participating in clinical research visit NIH Clinical Research Trials and You. Learn about clinical trials currently looking for people with microcephaly at

Where can I find more information about microcephaly?

More information about microcephaly may be available from the following resources:

Birth Defect Research for Children, Inc.
Phone: 407-895-0802

Genetic and Rare Diseases (GARD) Information Center

March of Dimes
Phone: 888-663-4637



The Arc of the United States
Phone: 202-534-3700 or 800-433-5255

Content source: Accessed June 23, 2023.

The information in this document is for general educational purposes only. It is not intended to substitute for personalized professional advice. Although the information was obtained from sources believed to be reliable, MedLink, its representatives, and the providers of the information do not guarantee its accuracy and disclaim responsibility for adverse consequences resulting from its use. For further information, consult a physician and the organization referred to herein.

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