Your doctor can measure your baby’s growth in several 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 sex. This condition may be present when your baby is born.

It may also develop in the first 2 years of their life. It has no cure. However, early diagnosis and treatment can improve your child’s outlook.

Most of the time, abnormal brain development causes this condition.

Abnormal brain development can occur while your child is still in the womb or during infancy. Often, the cause of abnormal brain development is unknown. Some genetic conditions can cause microcephaly.

Genetic conditions

Genetic conditions that can cause microcephaly include:

Cornelia de Lange syndrome

Cornelia de Lange syndrome slows your child’s growth inside and outside of the womb. Common characteristics of this syndrome include:

  • intellectual problems
  • arm and hand abnormalities
  • distinct facial features

For example, children with this condition often have:

  • eyebrows that grow together in the middle
  • low-set ears
  • a small nose and teeth

Down syndrome

Down syndrome is also known as trisomy 21. Children with trisomy 21 typically have:

Cri-du-chat syndrome

Babies with cri-du-chat syndrome, or cat’s cry syndrome, have a distinct, high-pitched cry, like that of a cat. Common characteristics of this rare 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 Rubenstein-Taybi syndrome are shorter than normal. They also have:

  • large thumbs and toes
  • distinctive facial features
  • intellectual disabilities

People with the severe form of this condition often don’t survive past childhood.

Seckel syndrome

Seckel syndrome is a rare condition that causes growth delays in and out of the womb. Common characteristics include:

  • intellectual disability
  • certain facial features, including a narrow face, beak-like nose, and sloping jaw.

Smith-Lemli-Opitz syndrome

Babies with Smith-Lemli-Opitz syndrome have:

Early signs of this disorder include:

  • feeding difficulties
  • slow growth
  • combined second and third toes

Trisomy 18

Trisomy 18 is also known as Edward’s syndrome. It can cause:

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

Babies with Trisomy 18 usually don’t survive past the 1st 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, using alcohol or drugs while pregnant can cause microcephaly in children.

The following are other potential causes of microcephaly:

Zika virus

Infected mosquitos transmit Zika virus to humans. The infection usually isn’t very serious. However, if you develop the Zika virus disease while you’re pregnant, you can transmit it to your baby.

Zika virus may cause microcephaly and several other serious birth defects. These include:

  • vision and hearing defects
  • 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 is 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 3 months of pregnancy, your baby may develop severe problems.

These problems can include:

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:

This parasite is found in some cat feces and uncooked meat.

Congenital cytomegalovirus

If you contract the cytomegalovirus while you’re pregnant, you can transmit it to your fetus through your placenta. Other young children are common carriers of this virus.

In infants, it can cause:

If you’re pregnant, you should take precautions, including:

  • washing your hands frequently
  • not sharing utensils with children under 6 years old

Uncontrolled phenylketonuria (PKU) in the mother

If you’re pregnant and have phenylketonuria (PKU), it’s important to follow a low-phenylalanine diet. You can find this substance in:

If you consume too much of phenylalanine, 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 developing this disorder.
  • Severe maternal malnutrition can also increase their chances of developing it.

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 sex.

Children with more severe complications may experience:

Dwarfism and short stature are not complications of microcephaly. However, they may be associated with the condition.

Your child’s doctor can diagnose this condition by tracking your baby’s growth and development. When you give birth to your baby, the doctor will measure their head circumference.

They’ll place a measuring tape around your baby’s head and record its size. If they note 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 2 years of life. They’ll also keep records of your child’s growth and development. This will help them detect any abnormalities.

Record any changes in your baby’s development that occur between visits with their doctor. Tell the doctor about them at the next appointment.

There’s no cure for microcephaly. However, treatment is available for your child’s condition. It will focus on managing complications.

If your child has delayed motor function, occupational therapy may benefit them. 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, the doctor may also prescribe medication to treat them.

If your child’s doctor diagnoses them with this condition, you’ll also need support. Finding caring healthcare providers for your child’s medical team is important. They can help you make informed decisions.

You may also want to connect with other families whose children are living with microcephaly. Support groups and online communities may help you manage your child’s condition and help you find useful resources.

It’s not always possible to prevent microcephaly, especially when the cause is genetic. If your child has this condition, you may want to seek genetic counseling.

Genetic counseling can provide answers and information relevant to life stages, including:

  • planning for pregnancy
  • during pregnancy
  • caring for children
  • living as an adult

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.

The Centers for Disease Control and Prevention (CDC) recommends that women who are pregnant shouldn’t travel to areas where there have been Zika virus outbreaks or areas that have a risk of Zika outbreaks.

The CDC advises women who are considering getting pregnant to follow the same recommendations or at least speak to their doctor before traveling to these areas.