What Causes Microcephaly?

Medically reviewed by George Krucik, MD on April 4, 2016 Written by Darla Burke

Your doctor can measure your baby’s growth in a number of ways. For example, your doctor will check your baby’s height or length and their weight to learn if they’re growing normally. Another measure of infant growth is head circumference, or the... Read More

Your doctor can measure your baby’s growth in a number of ways. For example, your doctor will check your baby’s height or length and their weight to learn if they’re growing normally. Another measure of infant growth is head circumference, or the size of your baby’s head. It’s important because it can indicate how well their brain is growing. If your baby’s brain isn’t growing properly, they may have a condition known as microcephaly.

Microcephaly is a condition in which your baby’s head is smaller than those of other children of the same age and gender. This condition may be present when your baby is born. It may also develop in the first two years of their life. It has no cure. Early diagnosis and treatment, however, can improve your child’s outlook.

What causes microcephaly?

This condition is caused by abnormal brain development. Abnormal brain development can occur while your child is still in the womb or during infancy. Genetic conditions can also contribute to the development of microcephaly.

Genetic conditions

Genetic conditions that can cause microcephaly include:

Cornelia de Lange syndrome

This disorder slows your child’s growth inside and outside of the womb. Severe intellectual problems, arm and hand abnormalities, and distinct facial features are common. For example, children with this condition often have eyebrows that grow together in the middle, low-set ears, and a small nose and teeth.

Down syndrome

This condition is also known as trisomy 21. Children with trisomy 21 typically have:

  • cognitive delays
  • mild to moderate intellectual disability
  • weak muscles
  • distinctive facial features, such as almond-shaped eyes, a round face, and small features

Cri du Chat syndrome

Babies with this condition have a distinct, high-pitched cry, similar to that of a cat. The common features of this syndrome include:

  • intellectual disability
  • low birth weight
  • weak muscles
  • certain facial features, such as wide-set eyes, a small jaw, and low-set ears

Rubinstein-Taybi syndrome

Babies with this rare condition are shorter than normal. They also have large thumbs and toes, distinctive facial features, and intellectual disabilities. People with the severe form of this condition often don’t survive past childhood.

Seckel syndrome

This rare condition causes growth delays in and out of the womb. Common characteristics include intellectual disability and certain facial features, including a narrow face, beaklike nose, and sloping jaw.

Smith-Lemli-Opitz syndrome

Babies with this condition have intellectual disabilities and behavioral disabilities that mirror autism. Early signs of this disorder include feeding difficulties, slow growth, and combined second and third toes.

Trisomy 18

This condition is also known as Edward’s syndrome. It can cause:

  • slow growth in the womb
  • a low birth weight
  • an irregularly-shaped head
  • organ defects

Babies with this condition usually don’t survive past the first month of life.

Exposure to viruses, drugs, or toxins

Microcephaly can also occur when your child is exposed to certain viruses, drugs, or toxins in the womb. For example, the use of alcohol or drugs by pregnant women can cause microcephaly in their children.

The following are other potential causes of microcephaly:

Zika virus

Zika virus spreads to humans through infected mosquitos. The infection usually isn’t very serious. However, if you develop the zika virus disease while you’re pregnant, you can pass it on to your baby. Zika virus causes microcephaly and several other serious birth defects. These include vision and hearing defects, and impaired growth.

Methylmercury poisoning

Some people use methylmercury to preserve the seed grain that they feed animals. It can also form in water, leading to contaminated fish. Poisoning occurs when you eat contaminated seafood or meat from an animal that’s been fed seed grain that contains methylmercury. If your baby becomes exposed to this poison, they may develop brain and spinal cord damage.

Congenital rubella

If you contract the virus that causes German measles, or rubella, within the first three months of pregnancy, your baby may develop severe problems. These problems can include deafness, intellectual disability, and seizures. However, this condition isn’t very common due to the use of the rubella vaccine.

Congenital toxoplasmosis

If you’re infected with the parasite Toxoplasma gondii while you’re pregnant, it can harm your developing baby. Your baby may be born prematurely with many physical problems, including seizures and hearing and vision loss. This parasite is found in some cat feces and uncooked meat.

Congenital cytomegalovirus

If you contract this virus while you’re pregnant, you can pass it on to your fetus through your placenta. Other young children are common carriers of this virus. It can cause jaundice, rashes, and seizures in infants. If you’re pregnant, you should take precautions by washing your hands frequently and not sharing utensils with children under age 6.

Uncontrolled phenylketonuria (PKU) in the mother

If you’re pregnant and have the gene for phenylketonuria (PKU), it’s important to follow a low phenylalanine diet. If you consume too much of this substance, which you can find in milk, eggs, and aspartame sweeteners, it can harm your developing baby.

Delivery complications

Microcephaly may also be caused by certain complications during delivery. Decreased oxygen to your baby’s brain can increase their risk of this disorder. Severe maternal malnutrition can also increase their chances of developing it.

What complications are associated with microcephaly?

Children diagnosed with this condition will have mild to severe complications. Children with mild complications may have normal intelligence. However, their head circumference will always be small for their age and gender.

Children with more severe complications may experience:

  • intellectual disability
  • delayed motor function
  • delayed speech
  • facial distortions
  • dwarfism, or short stature
  • hyperactivity
  • seizures
  • difficulty with coordination and balance

How is microcephaly diagnosed?

Your doctor can diagnose this condition by tracking your baby’s growth and development. When you give birth to your baby, your doctor will measure their head circumference. They’ll place a measuring tape around your baby’s head and record its size. If your doctor notes abnormalities, they may diagnose your child with microcephaly.

Your child’s doctor will continue to measure your child’s head at routine well-baby exams during the first two years of life. They’ll also keep records of your child’s growth and development. This will help your child’s doctor detect any abnormalities.

You should also record any changes in your baby’s development that occur between visits with their doctor and tell their doctor about them at the next appointment.

How is microcephaly treated?

There’s no cure for microcephaly. Treatment for your child’s condition will focus on managing complications.

If your child has delayed motor function, they may benefit from occupational therapy. If they have delayed language development, speech therapy may help. These therapies will help build and strengthen your child’s natural abilities. If your child develops certain complications, such as seizures or hyperactivity, their doctor may also prescribe medication to treat them.

What to do if your child is diagnosed with microcephaly

If your child’s doctor diagnoses them with this condition, you’ll need support. Finding a doctor and care team to help you make informed decisions is important. You may also want to connect with other families facing the same challenges. Support groups and online communities may help you manage your child’s condition and find useful resources.

Can microcephaly be prevented?

It’s not always possible to prevent microcephaly, especially when the cause is genetic. If you have a child with the condition, you may want to seek genetic counseling before having another child.

Getting proper prenatal care and avoiding alcohol and drug use while pregnant may help you prevent microcephaly. Prenatal checkups give your doctor the opportunity to diagnose maternal conditions, such as uncontrolled PKU.

Medically reviewed by George Krucik, MD on April 4, 2016 Written by Darla Burke

3 possible conditions

This feature is for informational purposes only and should not be used to diagnose. Please consult a healthcare professional if you have health concerns.

Medically reviewed by George Krucik, MD on April 4, 2016 Written by Darla Burke