14 Jul 2026
Cystic fibrosis (CF) remains one of the most common life-limiting autosomal recessive genetic conditions. Prenatal identification of at-risk pregnancies plays a critical role in early counseling, diagnostic planning, and care coordination. While new and emerging prenatal CF screening strategies, such as single-gene non-invasive prenatal testing (sgNIPT), may offer options in settings where standard testing is not feasible, many providers are re-evaluating these approaches due to documented limitations. According to the American College of Obstetricians and Gynecologists (ACOG), sgNIPT remains investigational. Partner testing and diagnostic testing are still required, despite claims of simplification.
sgNIPT studies have also acknowledged another major limitation: that sgNIPT may miss fetuses at risk for CF caused by the same variants. This is often referred to as “homozygous.” New research from Labcorp and Invitae helps put these limitations into perspective.
Data reveals that one in three individuals with homozygous cystic fibrosis transmembrane conductance regulator (CFTR) pathogenic variants carry mutations other than the common p.Phe508del variant. The gap is even wider among patients who self-report as non-white. These findings raise important considerations for the performance of sgNIPT approaches to cystic fibrosis prenatal screening, particularly in diverse populations.
A quick refresher: Prenatal CF screening today
When clinicians think about prenatal CF screening, most approaches fall into two categories.
Carrier screening, typically performed on one or both biological parents, evaluates whether they carry pathogenic variants in the CFTR gene. If both parents are carriers, diagnostic testing is offered and can be performed during pregnancy or after delivery.
sgNIPT approaches use the same type of cell-free DNA used for aneuploidy screening to assess fetal risk from only a pregnant patient’s blood sample.
In theory, this can streamline workflows and reduce the need for paternal testing. In practice, performance depends heavily on whether the fetal variant aligns with the algorithms built into the test. That is where limitations emerge.
Homozygosity in CF
The p.Phe508del variant, also known as F508del, is the most common disease-causing CFTR pathogenic variant in individuals of European ancestry. However, CFTR is a large gene with hundreds of pathogenic variants. The distribution of those variants is not uniform across populations.
What the Labcorp research shows
Labcorp researchers retrospectively analyzed CFTR genetic results from more than 450,000 individuals who underwent either diagnostic testing or carrier screening. Pathogenic CFTR variants were classified using ACMG-based criteria, with a focus on individuals who were homozygous for disease-causing variants.
The findings were striking:
- One in three individuals with homozygous CFTR pathogenic variants had variants other than p.Phe508del
- Among white individuals with homozygous CFTR variants, 92% were homozygous for p.Phe508del
- Among non-white individuals, only 43% were homozygous for p.Phe508del
- Non-p.Phe508del homozygous variants were disproportionately represented among Hispanic, Asian, Middle Eastern, and other non-white populations
In other words, reliance on sgNIPT strategies that are most sensitive to F508del homozygosity can miss at-risk fetuses homozygous for other CFTR variants, disproportionately favoring detection in white populations and increasing the risk of under-identification in others.
Why this matters for cfDNA screening performance
If a fetus carries a homozygous CFTR variant other than F508del, a sgNIPT approach may classify the pregnancy as low risk. This creates the potential for false-negative screening results.
From a clinical perspective, this means:
- At-risk pregnancies may not be flagged for confirmatory diagnostic testing, leading to a possible delay in fetal or postnatal therapies
- Counseling conversations may be incomplete or falsely reassuring, especially without a true understanding of the couple’s reproductive risk when partner testing is bypassed
- Disparities in detection may widen, particularly for non-white patients
For providers caring for increasingly diverse populations, this represents a meaningful gap in prenatal care.
The equity implications are hard to ignore
Healthcare equity is no longer a theoretical discussion; it is a daily reality in prenatal practice.
When screening tools perform better for some populations than others, even unintentionally, the outcome is unequal access to early information and informed pregnancy management.
The data suggests that some screening strategies may miss a substantial proportion of CF-affected pregnancies in non-white populations. That risk compounds existing disparities in access to genetic counseling, diagnostic testing, and specialty care.
For providers, the question is no longer the availability of prenatal CF screening, but whether newer screening strategies are performing equally well for all patients.
Rethinking what “effective” prenatal CF screening means
This research does not suggest that all cfDNA-based approaches are ineffective. Rather, it highlights the importance of understanding what a given test is designed to detect and what it may miss.
An effective prenatal CF screening strategy should account for the genetic heterogeneity of CFTR variants across the CF patient population and support equitable identification of at-risk pregnancies.
For clinicians evaluating prenatal CF screening options, these criteria may help guide conversations with laboratories, genetic counselors, and patients.
Using data to guide better prenatal conversations
When discussing prenatal CF screening with patients, especially those from ethnically diverse backgrounds, providers may consider:
- Reviewing the limitations in detecting at-risk fetuses with homozygous variants, particularly among patients more likely to carry non-F508del variants
- Determining if sgNIPT will be informative for known carrier-carrier couples, as this may be variant-dependent
- Discussing residual risk, even in the setting of a low-risk result
- Examining complementary approaches, such as comprehensive carrier screening or diagnostic testing, when appropriate
Data-driven transparency builds trust and supports shared decision-making.
Equity from screening to diagnosis
As prenatal testing continues to advance, performance alone is not the only benchmark that matters. Assessing real-world applicability across diverse populations is essential to making equitable and inclusive screening options available for all patients.
When it comes to a diagnosis of CF, multiple different genetic combinations are possible. For patients, a test’s ability to identify all possible variant combinations can make all the difference.