Merck Manual

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Last full review/revision Feb 2021| Content last modified Feb 2021
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What is microcephaly?

"Micro-" means small, and "-cephaly" refers to the head, so microcephaly is a small head.

  • A baby with microcephaly usually has a small brain, and the brain may not have formed properly

  • Microcephaly is rare

  • Microcephaly can be caused by many problems that occur in the womb, including infections, lack of oxygen, lack of proper nutrition, and birth defects of the brain

  • Doctors may find that the baby has microcephaly before birth when they do a routine ultrasound of the fetus

  • There's no cure for microcephaly, but therapy may help babies maximize their abilities

What causes microcephaly?

Causes of microcephaly include:

  • Infections in the mother during pregnancy, including rubella and Zika virus infection

  • Exposure to certain drugs or toxins before birth

  • Lack of oxygen before or during birth

  • Genetic problems, such as Down syndrome

What are the symptoms of microcephaly?

The baby has a noticeably small head. The other symptoms of microcephaly depend on how severely the brain is damaged or underdeveloped. Symptoms include:

  • Seizures

  • Developmental delays

  • Feeding problems

  • Hearing or vision problems

  • Problems with movement or balance

  • Hyperactivity 

  • Intellectual disabilities

How can doctors tell if a baby has microcephaly?

Doctors can tell if a baby has microcephaly when they do a routine ultrasound between the late 2nd and early 3rd trimester of pregnancy. If doctors suspect microcephaly once a baby is born, doctors will do:

How do doctors treat microcephaly?

There's no cure or standard treatment for microcephaly. Treatment may include:

  • Treating the symptoms from brain damage

  • Early intervention, which offers therapy to babies to improve their physical and mental abilities

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