Causes and Risk Factors of Craniosynostosis

The cause of craniosynostosis is unknown, but the condition may be a result of genetic and environmental factors. In rare cases, craniosynostosis is caused by a known genetic condition. A mother’s health and medication use may also impact a baby’s risk of craniosynostosis. 

Close-up of mother kissing baby daughter lying on bed at home

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Common Causes

It’s believed that craniosynostosis is caused by a defect in the hardening process of the skull (cranial) bones. The underlying cause of this defect is unknown and thought to be random. When the defect is caused by a genetic disorder, it is a result of a known mutation in a specific gene. 

There are two forms of craniosynostosis: syndromic and nonsyndromic. Syndromic craniosynostosis is part of a larger genetic syndrome, and nonsyndromic craniosynostosis occurs on its own without a known cause. 

Risk Factors

While the exact cause of craniosynostosis is unknown, researchers have determined that certain factors are associated with a greater risk of craniosynostosis. A fetus may be more likely to develop craniosynostosis depending on their position in the mother’s uterus.

Multiple babies, such as twins or triplets, are also at higher risk. A baby with a large head size may be more likely to experience craniosynostosis, as well.

Other known risk factors include:

  • Maternal thyroid disease: Women who develop or are being treated for thyroid disease during their pregnancies are at higher risk of having a baby with craniosynostosis.
  • Smoking: Women who smoke at least one pack of cigarettes per day are at increased risk of having a baby with craniosynostosis. There does not appear to be an increased risk during the first trimester, but women who smoke later into their pregnancies are at a higher risk of having a baby with craniosynostosis.
  • Fertility treatments: Women who took certain fertility medications, such as clomiphene citrate (Clomid), are more likely to have a baby with craniosynostosis.

The following characteristics are not considered risk factors, but have been associated with a diagnosis of craniosynostosis:

  • Male sex
  • Preterm babies
  • Maternal obesity
  • Non-Hispanic white mother


The majority of cases of craniosynostosis do not have a known cause and appear to be random. It’s estimated that about 8% of babies with craniosynostosis inherited the condition as part of a genetic disorder. When your child has a genetic disorder, it means that they inherited the genes from one or both parents.

Researchers believe that craniosynostosis is transmitted to a baby as an autosomal dominant trait. This abnormality in the gene leads to a disruption of the cells responsible for building bone called fibroblasts.

Mutations in the following genes may be associated with craniosynostosis:

  • TCF-12
  • ERF
  • CDC45
  • SMO
  • SMAD6

Genetic conditions that can cause or are associated with craniosynostosis include:

  • Antley-Bixler syndrome: A rare genetic condition that affects the skull and bones in the face
  • Apert syndrome: A genetic disorder that causes premature fusing of the bones in the skull (craniosynostosis), as well as in the fingers and toes
  • Carpenter syndrome: A genetic disorder that causes changes in the formation of the skull, fingers, and toes
  • Crouzon syndrome: A genetic disorder that affects the bones, muscles, joints, and cartilage, and often leads to the premature fusing of several sutures in the skull
  • Frontonasal dysplasia: A rare genetic disorder that leads to abnormal development of the head and face, including wide-set eyes, a flat nose, and a groove down the middle of the face 
  • Muenke syndrome: A genetic disorder that causes the premature fusing of the coronal suture, as well as other areas of the skull
  • Saethre-Chotzen syndrome: A genetic condition that causes premature fusing of the bones in the skull and face
  • Pfeiffer syndrome: A rare genetic disorder that causes a baby’s skull bones to fuse together


The cause of craniosynostosis is unclear, but researchers have linked some genetic mutations and certain lifestyle habits of the mother during pregnancy to this condition. Craniosynostosis may also occur along with a genetic disorder inherited from the parents.

Frequently Asked Questions

What chromosome causes craniosynostosis?

There is not one single chromosome to blame for craniosynostosis. While it is possible for the condition to be caused by a genetic disorder, the cause is often unknown. Mutations in several genes have been associated with craniosynostosis.

How is craniosynostosis diagnosed?

Craniosynostosis is often diagnosed at birth if your baby is born with a misshapen head. The condition may also be diagnosed at a well-child visit during your child’s first year of life. Craniosynostosis is diagnosed with a physical exam and a CT scan

What is craniosynostosis surgery?

Craniosynostosis surgery is performed to relieve any pressure on your child’s brain and to reshape the head into a more circular shape. In one type of surgery called calvarial vault remodeling, your child’s surgeon will make an incision in their scalp and correct the head’s shape by moving the bones in the skull.

How long does it take babies to adjust to a helmet for craniosynostosis?

Each baby is different and will adjust to the treatment helmet in their own time. If your baby requires a helmet for shaping their head due to craniosynostosis, your specialist will most likely recommend that they wear it for 23 hours a day, including while sleeping. Your little one will need frequent follow-up visits with their helmet specialist to monitor their head shape and progress.

A Word From Verywell

Craniosynostosis is a relatively common birth defect that does not always have a known cause. The condition may be associated with a genetic disorder, environmental risk factor, or a combination of the two. Maternal risk factors for craniosynostosis include thyroid disease, smoking, and the use of fertility treatments. 

Even though some of the risk factors are related to the mother’s health, you did not cause your child’s condition, and you are not to blame. Craniosynostosis is a complicated condition with several possible causes.

If you are concerned that you have one of the known risk factors during your pregnancy, talk with your doctor about any changes you can make, as well as about undergoing genetic counseling.

10 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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  6. Schraw JM, Woodhouse JP, Langlois PH, et al. Risk factors and time trends for isolated craniosynostosis. Birth Defects Res. 2021;113(1):43-54. doi:10.1002/bdr2.1824

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By Carrie Madormo, RN, MPH
Carrie Madormo, RN, MPH, is a health writer with over a decade of experience working as a registered nurse. She has practiced in a variety of settings including pediatrics, oncology, chronic pain, and public health.