Causes of Microcephaly

Microcephaly is a congenital condition in which the newborn baby’s head is abnormally small head for his or her age or stage of development. Although microcephaly does not always have an impact beyond this physical sign, the extent to which a child experiences the condition can vary from mild to severe.

The disease can have an impact on the child’s development, both physical and mental, as well as his or her life expectancy. In some children, microcephaly is congenital while in others it can develop during childhood.

There are 41 different types of the microcephaly. Depending on the trigger factors, the disease can impact a child’s intelligence, movement, speech, and other physical aspects such as sight and hearing. The disease can affect both males and females in all parts of the world.

Various causes of microcephaly include the following:


Viruses can cause brain developmental issues as well as cell death which can lead to microcephaly. There are a number of viruses that can trigger the disease. If a pregnant woman has rubella, also known as German measles, it can cause congenital microcephaly in the developing child alongside other symptoms such as eye, hearing, and heart issues. German measles is identifiable by the red rash of tiny spots that cover the skin, high temperature, swollen glands, aches and pains, as well as cold symptoms.

If a pregnant woman contracts the congenital cytomegalovirus infection, her child has a high chance of contracting the virus too. This can cause neurological issues in infected fetuses leading to microcephaly.

Similarly, pregnant women infected with the varicella-zoster virus, which causes chicken pox - an itchy condition characterized by spots on the face, belly, chest, arms, and legs,  can pass the infection on to the developing fetus, which can lead to many neurological problems including microcephaly.

A recent outbreak of Zika virus in Brazil has been linked to a spike in the number of cases of microcephaly in newborns, showing that infected pregnant women can pass the virus onto the baby. This virus is transmitted to humans by infected Aegypti mosquitoes and this recent discovery calls for more focus on the symptoms and prognosis of microcephaly.


Scientists have observed that a poor diet in mothers during pregnancy can lead to microcephaly in newborn babies. The effect is irreversible in the developing child as noted in a study involving aboriginal children in Australia.

Drugs, alcohol and toxic chemicals

Abuse of drugs and alcohol during pregnancy can stunt the development of a child’s brain in the womb and result in microcephaly. Exposure to other toxic chemicals during pregnancy has a similar effect in babies.


A condition called craniosynostosis in which bones in the skull start to fuse together while the infant is still growing can prevent the brain from developing properly. The child can undergo an operation to correct the issue, before it becomes extremely serious, to provide the brain with enough space to develop properly.

Conditions caused by chromosome abnormalities

Down’s Syndrome and other diseases resulting from chromosome abnormalities can trigger microcephaly.


A pregnant mother with phenylketonuria - caused by the lack of phenylalanine hydroxylase enzyme activity - can have phenylalanine building up to dangerous levels in the blood and brain. This can be passed on to the developing child and stunt the development of his or her brain resulting in microcephaly. The risk tends to be higher after birth than before as the mother is often able to break it down during pregnancy. The problem starts once the newborn begins feeding. It is detected by taking blood samples of the baby a day or two after birth.

Lack of oxygen (cerebral anoxia)

Reduced oxygen supply to the baby’s brain due to any reason during pregnancy and delivery can also result in microcephaly.


Further Reading

Last Updated: Dec 30, 2022

Deborah Fields

Written by

Deborah Fields

Deborah holds a B.Sc. degree in Chemistry from the University of Birmingham and a Postgraduate Diploma in Journalism qualification from Cardiff University. She enjoys writing about the latest innovations. Previously she has worked as an editor of scientific patent information, an education journalist and in communications for innovative healthcare, pharmaceutical and technology organisations. She also loves books and has run a book group for several years. Her enjoyment of fiction extends to writing her own stories for pleasure.


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