In the early stages of pregnancy, and sometimes even pre-conception, parents are offered a variety of options to learn about their baby’s development through screens and tests. Carrier screening is a common one that medical experts recommend. One of the conditions that can be included in a carrier screen is fragile X syndrome.

Babies affected by fragile X have a chance for better outcomes when the condition is identified early, and they can begin treatments early. 

What is fragile X syndrome?

Fragile X syndrome (FXS) is a genetic condition that is one of the most common causes of genetically inherited intellectual disability. FXS occurs in about 1 in 7,000 males and 1 in 11,000 females.1

Signs that a child might have FXS include developmental delays, learning disabilities, and social and behavioral problems. Males with FXS often have intellectual disabilities that can range from mild to severe. Females, who often have milder symptoms, can have typical intelligence or some degree of intellectual disability. Autism spectrum disorder also occurs more frequently in people with FXS.1

Delays in diagnosing and treating FXS

For children diagnosed with FXS, the FRAXA Research Foundation recommends early intervention to help young kids work toward meeting their developmental milestones. Early intervention focuses on building physical, cognitive, communication, self-help, and social/emotional skills.2

Although children with FXS can benefit from early intervention and treatment, they may not get these benefits if they are not diagnosed early.

Parents, pediatricians, and early educators frequently see early developmental differences in infants and toddlers with FXS. Yet the average age of diagnosis with FXS is not until around age three, because it can take that long to understand the cause of this collection of symptoms. Males tend to be diagnosed a little earlier than females because symptoms in males tend to be more noticeable. Symptoms in females are typically less severe. Families who have a child with FXS often describe going through a “diagnostic odyssey.”3

This delay in properly diagnosing FXS can negatively affect the benefits a child may gain through earlier medical support.

Screening for FXS earlier

One way to identify the chance for FXS earlier is through non-invasive carrier screening, which requires just a small sample of your saliva or blood. You can have carrier screening for FXS done early in your pregnancy or before you even become pregnant. Results are typically available in about two weeks.

By screening for FXS before becoming pregnant or early in your pregnancy, you will have important information to make informed decisions with the help of your healthcare provider.

Since it is rare, in most cases, screening for fragile X syndrome will show that your baby does not have an increased chance to have FXS. But if your screening identifies you as a carrier of FXS, you can have additional diagnostic tests, like preimplantation genetic testing, amniocentesis, or chorionic villus sampling to find out if your child is affected. You will also have time to find fragile X experts and line up early intervention for your child.

Among caregivers who have a child with fragile X syndrome, researchers found that when presented with a range of possibilities for identifying FXS, 79% preferred preconception carrier screening over other times and ways of identifying FXS. The reason: Carrier screening before conception provides more options when making reproductive decisions.4

Early screening and intervention with certain conditions can make a huge impact on your child’s future health. Because of this, the American College of Obstetricians and Gynecologists recommends that your healthcare provider gives you information about carrier screening.5 If you are thinking about becoming pregnant, you can proactively discuss this with your provider. If you are already pregnant, click here to find out how to get screened.

References

1. CDC. Fragile X syndrome (FXS). https://www.cdc.gov/fragile-x-syndrome/about/index.html. Accessed April 10, 2025.

2. Morin A. What is early intervention? Understood. https://www.understood.org/en/articles/early-intervention-what-it-is-and-how-it-works. Accessed April 10, 2025

3. Okoniewski KC, Wheeler AC, Lee S, et al. Early identification of Fragile X syndrome through expanded newborn screening. Brain Sci. 2019;9(1),4. https://doi.org/10.3390/brainsci9010004.

4. Bailey Jr. DB, Bishop E, Rapsa M, Skinner D. Caregiver opinions about Fragile X population screening, Genetics in Medicine. 2012;14(1): 115-121.

5. Carrier screening for genetic conditions. Committee Opinion No. 691. American College of Obstetricians and Gynecologists. Obstet Gynecol 2017;129:e41–55.

6. Morris JK, Law MR, Wald NJ. Is cascade testing a sensible method of screening a population for autosomal recessive disorders?. Am J Med Genet A. 2004;128A(3):271-275. doi:10.1002/ajmg.a.30024.

Reviewed by Tiana Francy, MSc

Tiana Francy holds advanced degrees in both Molecular Genetics and Science Education. She spent over a decade researching genetic causes of disease and developing and validating lab tests to further the advancement of precision medicine. She currently serves as a Medical Science Liaison at Myriad Genetics bridging the gap between the intricacies of genetic medicine and the providers who administer it.

Need help talking to your doctor about getting screened?

Learn about the screening process and how to talk to your doctor.

How to get screened
What are inherited genetic conditions?

Through your genes, you will pass on physical traits to your child, such as eye and hair color, blood type, and more. Some health conditions and predispositions to certain diseases are also passed on genetically.

The term “inherited conditions” refers to inherited genetic health conditions that a parent might pass on to a child. Most babies with genetic diseases are born to parents with no known family history of that disease.6 It is normal to be a carrier for an inherited condition; many of us are and we just don’t know it.

For many conditions, being a carrier means you inherited one working gene and another gene with a change that causes it not to work correctly. Since you have one working gene, you typically don’t have any symptoms.

However, if both parents have a change in the same gene, then there’s a 25% chance that your baby will inherit both changes and develop symptoms. When a genetic condition is related to a gene on the X-chromosome, it is referred to as an X-linked condition. The inheritance of X-linked conditions is more complex than most conditi ons. The odds of a baby having an X-linked condition can vary widely depending upon a number of factors including whether mom or dad carries the change, and whether their baby is male or female.