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What is microcephaly?

Microcephaly simply means 'small head'. Those with microcephaly have a head that is smaller than expected. It occurs as a result of abnormal brain development. This can happen while the baby is still in the mother's womb or within the first few years of birth.

What causes microcephaly in a baby?

About 2% of babies have microcephaly. It may develop in the womb (congenital) or during the first years of life as a consequence of the baby's brain being exposed to something that harms its growth and development.

Some causes of microcephaly include:

  • Viral infections, such as rubella (German measles), chickenpox, cytomegalovirus (a type of herpes virus), and possibly the Zika virus
  • Parasite infections, such as toxoplasmosis
  • Toxic chemicals, such as lead
  • Malnutrition in which the baby is not getting enough food or nutrients
  • Alcohol
  • Drugs
  • Haemorrhage or stroke in the newborn
  • Injury to the brain, or lack of oxygen to the brain, during or after birth
  • Spine or brain defects
  • Chromosomal abnormalities, such as Down's syndrome


Your doctor can make a diagnosis of microcephaly before or after the baby is born. A routine ultrasound scan offered between 18 and 21 weeks of pregnancy as part of a normal antenatal check can show if the baby has a smaller head size than expected.

After the baby is born, a midwife or other health care provider will measure around the widest part of the baby's head and record it on the baby's growth chart in the personal child health record (the 'red book'). If this measurement falls below a certain point on the growth chart, the baby will be considered to have microcephaly. The growth of the baby's head will be checked again during routine health and development reviews during the baby's early years.

What are the symptoms of microcephaly in a child?

If a baby has a mild case of microcephaly, there may be no other symptoms other than the baby having a small head, and although it will always be smaller than average, it will grow as the baby gets older. Some children with microcephaly have normal intelligence, however others will have learning problems. These won't get progressively worse as the child grows, but they will always be present.

Other possible symptoms in a child with microcephaly include:

  • Balance and coordination problems
  • Developmental delays such as delays in sitting, standing and walking
  • Trouble swallowing and problems with feeding
  • Hearing loss
  • Hyperactivity, with difficulty in sitting still or paying attention
  • Seizures
  • Short height
  • Speech problems
  • Vision problems


How is microcephaly managed?

There is no cure for microcephaly, but medication and therapies can help manage development and behaviour problems as well as medical conditions such as seizures.

How well the child does can depend on the reason the brain stopped growing in the first place. A child with mild microcephaly will need regular doctor check-ups to monitor how they grow and develop but otherwise may not require medical intervention. They may grow normally during childhood and adolescence and still meet age-appropriate growth milestones as they get older.

WebMD Medical Reference

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