What is microcephaly?

Microcephaly is a condition in which a baby’s head is smaller than average for an infant’s size and age. The baby is either born with a smaller head (congenital), or the condition develops as the baby gets older (acquired). Microcephaly is rare, occurring in 2-12 babies per 10,000 births.

What causes microcephaly?

The exact causes of microcephaly are not known. Microcephaly occurs most often because the brain fails to grow at a normal rate. This can be caused by a variety of conditions or by exposure to harmful substances while the baby is in the womb. Some of these causes include:

  • Genetic (inherited) disorders such as Down syndrome
  • Viral infections in the mother, such as rubella (German measles), toxoplasmosis (an infection caused by a parasite), cytomegalovirus (a common virus that can cause health problems for babies in the womb), and Zika virus (a virus transmitted by mosquitoes)
  • Alcoholism or drug abuse in the mother
  • Gestational diabetes
  • Poisoning from mercury or other metals or poisons
  • Maternal malnutrition (the mother doesn’t get enough food or nutrients while pregnant)

Acquired microcephaly might occur after birth because of various brain injuries caused by a lack of oxygen or infection.

What are the symptoms of microcephaly?

Aside from a noticeably smaller head, the following are the most common symptoms of microcephaly:

  • A high-pitched cry
  • Feeding problems
  • Hearing and vision problems
  • Convulsions (seizures)
  • Increased movement of the arms and legs (spasticity)
  • Hyperactivity (overly active)
  • Developmental delays, or problems learning how to speak, stand and walk
  • Intellectual disabilities (trouble with learning)

As the child grows older, his or her face continues to grow while the skull does not. This causes the child to develop a large face, a receding forehead and a loose, often wrinkled scalp. The rest of the body is often underweight and smaller than normal.

Some babies have no visible or noticeable symptoms. Also, some children who have microcephaly go on to develop normally.

Last reviewed by a Cleveland Clinic medical professional on 01/09/2019.

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