Fragile X Screening

By on October 19, 2021

There are a host of genetic conditions that parents can pass on to their children that can affect their pregnancy care and even how their child is predicted to develop. One condition predominantly affects boys, patients with XY chromosomes, but sometimes affects girls as well is called Fragile X syndrome. It’s a genetic condition that we screen for during early pregnancy testing and pre-conception carrier screening. Although children born with Fragile X syndrome survive into adulthood without major medical issues, they will almost certainly have some degree of behavioral and learning issues. It’s helpful to know about the condition ahead of time to plan for pregnancy or to prepare for the care of their child’s potential healthcare needs.

What is Fragile X Syndrome?

Fragile X syndrome is a genetic disorder of the X chromosome that causes intellectual disabilities and potential behavior issues, or even autism. Fragile X syndrome is linked to a specific gene sequence on the X chromosome where a section of code is normally made up of about fewer than 40 short, repeating segments of nucleotides (the building blocks of genes), but in Fragile X, the number of repeats totals more than  200.

The reason it primarily affects biological males (patients with XY sex chromosomes) is that they typically have only one X chromosome, whereas biological females usually have two. The condition is usually milder in XX or female patients since they have one normal and one expanded copy of the gene. However, in patients with only one X chromosome, with a full expansion mutation, the condition is more severe.

In addition to affecting children, women who are carriers for Fragile X syndrome can face serious health concerns. As many as one in five of those who carry a Fragile X premutation (56-199 repeats)  face a risk for premature ovarian insufficiency. This is essentially early onset menopause, where an affected person’s fertility is lower than it should be. People who are carriers for Fragile X can also develop a Parkinson’s-like condition known as Fragile X tremor-atraxia syndrome, in their 60s or later.

Risk Factors for Fragile X

As mentioned, Fragile X syndrome occurs when there’s an unusually high number of repetitions within  the FMR1 gene on the X chromosome. However, there’s no hard cut-off for how many is too many — the risk of passing the condition down or having it affect your child is predicted based upon the number of repeats found in the gene.

As Dr. Tamar Goldwaser explained in a recent Healthful Woman podcast, “As long as your [gene] is under 45 repeats, you’re considered to not be a carrier. When you have 45 until 54 repeats, it’s called an intermediate allele. And then when you have 55 all the way up to 199, it’s called a premutation allele.”

These levels stop at 199 because at 200, the body completely shuts down the gene, resulting in children with Fragile X syndrome. Before that level, children can have any number of repetitions and they won’t have the condition, save for a few potential side effects.

Repetitions of the genetic sequence can increase with each generation — a mother can pass the condition on to a daughter who has one healthy X and one slightly expanded X, with more repeats, who then may be more likely to pass it on to her children with more repetitions.

When to Get Screened for Fragile X

People can have screenings for genetic conditions such as Fragile X both before being pregnant as well as early in pregnancy. People who want to know as much as possible before their decision to try to become pregnant often use genetic screenings and screenings for other health conditions to get a better handle on what they could be in for during and after pregnancy. Fragile X screening is not required but can help provide answers ahead of time before finding out about certain genetic disorders after birth.

Fragile X Syndrome Counseling

It’s important to seek out serious genetic counseling if you find out you’re at risk for passing on Fragile X. First off, the sheer number of risk factors to consider when trying to figure out if you may pass on the condition to a baby is hard to comprehend without a professional guiding you through the numbers. Second, every person’s journey through pregnancy and life is different, and there are several options for parents who find out they may need to pursue alternatives to natural conception such as in-vitro fertilization or preserving eggs.

As Dr. Nathan Fox says, “you want it to be someone who can give you personalized, individualized counseling based on all of the relevant factors because there’s a lot.”

A genetic counselor can explain in detail and in real-world terms what the results of a Fragile X screening mean. They can also answer questions about future generations of children, and your pregnancy plans, whether the screening is done before conception or after.

Pre-Conception Counseling in New York City

At Maternal Fetal Medicine Associates, we provide a full array of genetic screenings for new parents or those who are considering trying for a baby, to provide them with as much confidence and awareness about their future children. Fragile X is one of dozens of genetic conditions that can affect both the mother and the baby, so it’s helpful to know ahead of time whether you may be carrying this condition. Schedule your appointment by calling our New York office or contacting us online today.

Maternal Fetal Medicine blogs are intended for educational purposes only and do not replace certified professional care. Medical conditions vary and change frequently. Please ask your doctor any questions you may have regarding your condition to receive a proper diagnosis or risk analysis. Thank you!

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