Maternal Fragile X Carrier: NEXT STEPS

Today, we’re diving into a topic that has completely transformed prenatal care over the past decade—non-invasive prenatal testing, or NIPT. Thanks to recent technological leaps, cfDNA, cell-free fetal DNA, is giving us unprecedented visibility through just a simple maternal blood draw. Take Fetal Focus by Natera, for example, or the UNITY Reflex Screen from BillionToOne. These options offer single-gene NIPT that can evaluate fetal risk for specific autosomal recessive conditions, like cystic fibrosis, spinal muscular atrophy, or sickle cell disease, to better risk stratify the fetus without going immediately to an invasive diagnostic test. Similarly, The UNITY CONFIRM option also evaluates whether a fetus is at low or high risk for fetal aneuploidies—chromosomal conditions like Trisomy 21, 18, and 13 up to a set gestational age as an alternative to amniocentesis, although that is still considered a screening test. That specialized test uses intact circulating fetal cells to non-invasively help assess aneuploidy risk without an immediate invasive procedure. But what happens when the maternal carrier screen comes back positive for a complex genetic variant, specifically a Fragile X mutation (an FMR1 gene expansion)? Should that automatically trigger a referral for diagnostic testing? In this episode, we’re going to cover exactly how Fragile X inheritance works, why current non-invasive technologies hit a wall with repeat expansion disorders, and what clinical decision steps patients and providers need to take next.

1. Carrier Screening for Genetic Conditions; ACOG CO NUMBER 691. MARCH 2017

(REAFFIRMED 2025)

2. https://utswmed.org/medblog/fragile-x-syndrome-pregnancy/