The condition presents as having a smaller than average head size as compared to babies who fall into the same age and sex categories. Microcephaly often results in a smaller brain size.1,2
Abnormal brain development frequently accompanies microcephaly and is often present in combination with other major birth defects, although it can also be the only abnormality present.1,2
Microcephaly can be present at birth due to abnormal brain growth in utero or may be diagnosed after birth as a result of poor brain growth.1,2
Here are some key points about microcephaly. More detail and supporting information is in the main article.
- Microcephaly is a rare condition, affecting 2-12 of every 10,000 live births in the US every year
- The condition can be present at birth or develop afterward
- The risk of microcephaly is increased by exposure to infections such as rubella during pregnancy
- Microcephaly is often accompanied by other serious medical conditions such as seizures, developmental delay and balance problems
- The severity of microcephaly and its symptoms varies from person to person
- Microcephaly can be diagnosed with an ultrasound scan during pregnancy
- There is currently concern over the possible link between the Zika virus and its relationship with the development of microcephaly.
The cause of microcephaly is not fully understood. However, there are certain conditions which may predispose an infant to develop the condition.1
Microcephaly can be present at birth following abnormal brain development in the uterus.
Conditions that pose a risk for developing microcephaly include:1,2
- Genetic or chromosomal abnormalities such as Down syndrome
- Infections such as rubella, toxoplasmosis, cytomegalovirus, chickenpox and possibly the Zika virus
- Severe malnutrition
- Craniosynostosis (premature skull suture line fusing)
- Cerebral anoxia (decreased oxygen delivery to the fetal brain)
- Maternal uncontrolled phenylketonuria (PKU), a birth defect that restricts the body's ability to break down a specific amino acid.
Environmental factors can also increase the risk of microcephaly. If a fetus is exposed to drugs, alcohol or toxins while in the womb, the risk of the baby developing a brain abnormality is higher.2
Infants with microcephaly will have a significantly smaller than average head size based on measurements of children in the same age and sex category. The size of the head is determined by measuring the circumference around the top of the head.1,2
While some children are born with small heads, children with microcephaly are significantly smaller than the average, and can even be smaller than the first percentile for an age group.2
Another characteristic feature - typically seen in more severe cases of microcephaly - is a backward-sloping forehead.2
Serious complications secondary to microcephaly can be serious and lifelong; at times, secondary conditions can be life-threatening.1
Complications of microcephaly include:1,2
- Developmental delays
- Facial distortions
- Movement and balance disorders
- Feeding problems
- Hearing loss
- Vision problems.
Ultrasound scanning during the second or third trimester can sometimes reveal microcephaly before birth.
Occasionally, the presence of microcephaly can be seen on a second or third trimester ultrasound and diagnosed prior to birth.1
To obtain a diagnosis of microcephaly after birth, the child will undergo a comprehensive examination process.
The diagnostic process for microcephaly can include:2
- A physical exam, including head circumference evaluation
- Prenatal examination
- Birth examination
- Taking a family history and evaluating the parents' head sizes
- Charting head growth over time.
CT scan and MRI will also provide the health care team with information regarding the presence of an infection in utero that may have caused structural brain changes.1
There is currently no treatment or cure for microcephaly. Instead, treatment focuses on interventions to manage the condition and alleviate accompanying conditions such as seizures.1,2
Mildly microcephalic babies typically only require routine check-ups. Those with a more severe form of the condition, however, may require early childhood intervention programs to strengthen and maximize the child's physical and intellectual capabilities, including speech, physical and occupational therapies.1,2
A condition called craniosynostosis can cause microcephaly. In cases of craniosynostosis, the joints between the bones of a baby's skull fuse together prematurely, preventing the brain from growing properly. However, this condition is typically reversible with surgery to help reshape the skull.2,3
Speak with your health care provider about your personal risks for having a baby with microcephaly and what you can do to lower that risk. In any pregnancy, it is important to reduce the risk of complications by avoiding the consumption of alcohol, drugs and other toxins.
Possible connection between microcephaly and Zika virus
Due to the recent concern over the risk of microcephaly and Zika virus, the CDC recommend that pregnant women avoid travel to regions affected by the spread of the Zika virus. These regions include:3
- Cape Verde
- El Salvador
- French Guiana
- Saint Martin
- Puerto Rico
- US Virgin Islands
- Dominican Republic.
"Travel to regions with ongoing Zika virus outbreaks is not recommended for women who are pregnant or women who are considering pregnancy," said Dr. Mark DeFrancesco, President of the American College of Obstetricians and Gynecologists, in a statement supporting the travel guidelines set in place by the CDC.4
To learn more about the CDC's travel recommendations, please visit their travel health notices web page.
The Brazilian authorities are investigating thousands of suspected cases of microcephaly in babies born to mothers infected with the mosquito-borne virus Zika while they were pregnant.
In Nature Communications, scientists at the Institute for Research in Biomedicine (IRB Barcelona) provide molecular details about Seckel Syndrome, a rare disease that causes microcephaly, or small brain, and growth delays.