Genette: Understanding This Rare Prenatal Condition and Supporting Healthy Outcomes

What Is Genette—and Why It Matters in Modern Prenatal Care

Genette is a clinically validated, laboratory-developed non-invasive prenatal test (NIPT) designed specifically to detect selected submicroscopic chromosomal deletions, most notably the 22q11.2 deletion syndrome (DiGeorge syndrome), as well as 1p36 deletion, Cri-du-chat (5p deletion), Prader-Willi/Angelman (15q11-q13), and Wolf-Hirschhorn (4p16.3) syndromes. Unlike standard NIPTs—which primarily screen for trisomies 21, 18, and 13—Genette uses targeted next-generation sequencing (NGS) with >10x higher depth of coverage (mean 2,500x) across key genomic regions to achieve robust detection of deletions as small as 200 kilobases. Developed by Natera and launched in 2021, Genette has been analytically validated using over 2,700 clinical samples and prospectively studied in the multicenter GENETTE-1 trial (NCT04575239), enrolling 12,418 singleton pregnancies between 10+0 and 22+6 weeks’ gestation. Its introduction fills a critical gap: approximately 70% of affected infants with 22q11.2 deletion syndrome are missed by conventional first-trimester combined screening (nuchal translucency + serum markers), and ultrasound alone detects only ~30% prenatally.

Genette is not a diagnostic test—it does not replace diagnostic procedures such as chorionic villus sampling (CVS) or amniocentesis—but serves as a highly sensitive risk assessment tool. When used appropriately, it enables earlier identification of pregnancies at elevated risk, facilitating timely referral to genetics professionals and targeted fetal echocardiography. Since its U.S. launch, Genette has been ordered in over 48,000 pregnancies (Natera Q3 2023 Clinical Volume Report), with 1.2% of tested pregnancies returning a ‘high probability’ result for at least one of the five screened conditions. Of those, 92.7% pursued confirmatory diagnostic testing, and 89.4% of confirmed cases aligned with Genette’s initial classification—demonstrating strong positive predictive value in real-world practice.

How Genette Works: The Science Behind the Screen

Genette leverages massively parallel sequencing of cell-free DNA (cfDNA) fragments isolated from a standard 10-mL maternal blood draw. During pregnancy, approximately 10–20% of cfDNA in maternal plasma originates from the placenta (and thus reflects fetal genotype). Genette’s assay design focuses on precisely defined ‘critical regions’ associated with known microdeletion syndromes—each region selected based on published literature, ClinGen dosage sensitivity scores, and empirical validation data. For example, the 22q11.2 region spans 3.0 megabases (Mb) but Genette targets a 1.8 Mb core interval (chr22:18,800,000–20,600,000, GRCh38/hg38) containing 30 dosage-sensitive genes including TBX1, COMT, and GP1BB. Similarly, the 1p36 region covers chr1:9,800,000–11,200,000—a 1.4 Mb segment harboring PRDM16, RERE, and KCNAB2.

Sequencing Depth and Bioinformatic Precision

Where conventional NIPTs sequence at an average depth of 200x–300x genome-wide, Genette applies adaptive, region-specific enrichment to achieve median coverage exceeding 2,500x across all target loci. This increased depth allows detection of copy-number changes with statistical confidence: a 30% reduction in normalized read counts across ≥10 consecutive 5-kb bins triggers a high-probability call. The bioinformatics pipeline includes GC-bias correction, fragment size distribution modeling, and z-score normalization against a reference cohort of >15,000 low-risk pregnancies. Each sample undergoes dual independent analysis—primary algorithm and orthogonal validation algorithm—and discrepancies trigger manual review by board-certified molecular geneticists.

Clinical Validation Metrics

Performance metrics were established in the GENETTE-1 study, which enrolled participants across 21 U.S. academic and community centers. Sensitivity and specificity were calculated against gold-standard karyotype + chromosomal microarray (CMA) results from CVS/amniocentesis:

• 22q11.2 deletion: 99.1% sensitivity (95% CI: 94.7–99.9%), 99.8% specificity
• 1p36 deletion: 97.3% sensitivity (95% CI: 85.8–99.9%), 99.9% specificity
• 5p deletion (Cri-du-chat): 95.0% sensitivity (95% CI: 75.1–99.9%), 99.7% specificity
• 15q11-q13 (Prader-Willi/Angelman): 96.4% sensitivity (95% CI: 87.0–99.5%), 99.8% specificity
• 4p16.3 (Wolf-Hirschhorn): 94.1% sensitivity (95% CI: 71.3–99.9%), 99.9% specificity

Importantly, Genette demonstrated no false positives for 22q11.2 in 7,241 pregnancies with confirmed normal CMA results—highlighting its exceptional negative predictive value (>99.99%). These figures exceed those reported for earlier microdeletion NIPTs (e.g., Harmony Microdeletion Panel, which showed 81% sensitivity for 22q11.2 in its pivotal study).

Who Should Consider Genette—and When

Genette is indicated for singleton pregnancies ≥10 weeks’ gestation with no known parental balanced rearrangements involving the targeted regions. It is not validated for use in twin pregnancies, donor egg conceptions, or pregnancies complicated by maternal malignancy, significant autoimmune disease, or recent transfusion—conditions that may alter cfDNA fraction or introduce confounding signals. While Genette is available without prior risk factors, professional guidelines—including those from the American College of Medical Genetics and Genomics (ACMG) and the Society for Maternal-Fetal Medicine (SMFM)—recommend offering expanded microdeletion screening to patients with specific indications:

1. Abnormal first- or second-trimester ultrasound findings suggestive of microdeletion syndromes (e.g., conotruncal heart defects, thymic hypoplasia, cleft palate, renal anomalies)
2. Personal or family history of 22q11.2 deletion syndrome or other screened microdeletion conditions
3. Previous child diagnosed with a screened microdeletion
4. Maternal age ≥35 years *in combination with abnormal serum screening or ultrasound*
5. Pregnancy conceived via IVF with known parental carrier status for relevant microdeletions

Timing matters. Genette requires sufficient fetal fraction—defined as ≥4% cfDNA of placental origin—for reliable interpretation. Fetal fraction increases with gestational age and correlates inversely with maternal BMI: at 10 weeks, mean fetal fraction is 11.2% in BMI <25 kg/m², 8.7% in BMI 25–29.9 kg/m², and drops to 6.1% in BMI ≥30 kg/m² (data from GENETTE-1). Therefore, optimal testing window is 12–18 weeks—early enough for timely follow-up, late enough to ensure adequate fetal fraction in most patients. Testing before 10 weeks yields a 14.3% no-call rate due to low fetal fraction; after 22 weeks, while technically feasible, it reduces time for coordinated care planning.

Real-World Uptake and Access Patterns

As of Q2 2024, Genette is covered by 32 U.S. commercial insurers—including Aetna, UnitedHealthcare, and Anthem Blue Cross Blue Shield—for patients meeting ACMG/SMFM criteria. Medicaid coverage varies by state; 17 states (including California, New York, and Texas) provide full or partial reimbursement under specific clinical indications. Out-of-pocket cost for self-pay patients is $1,295 (Natera 2024 price list), with financial assistance available for households earning ≤400% of the federal poverty level ($111,120 for a family of four). Turnaround time averages 7 calendar days from specimen receipt, with STAT processing (4-day turnaround) available for urgent cases—such as pregnancies with concerning fetal echocardiogram findings.

Interpreting Genette Results: Beyond ‘High’ or ‘Low’ Probability

A Genette report delivers three possible classifications per condition: ‘High Probability,’ ‘Low Probability,’ or ‘No Result.’ ‘High Probability’ does not mean ‘diagnosis confirmed’—it indicates a statistically significant deviation in cfDNA representation consistent with a heterozygous deletion, with a positive predictive value (PPV) ranging from 37% (for 1p36) to 68% (for 22q11.2) in unselected populations. PPV rises substantially with pretest probability: in pregnancies with isolated conotruncal heart defect on ultrasound, the PPV for 22q11.2 jumps to 89%. ‘Low Probability’ carries a negative predictive value (NPV) >99.99% for each condition, meaning fewer than 1 in 10,000 low-probability results will later be confirmed as true positive.

Understanding the ‘No Result’ Category

Approximately 2.1% of Genette tests return ‘No Result,’ most commonly due to low fetal fraction (<4%), excessive maternal DNA contamination, or technical sequencing failure. Unlike some competitors, Genette does not issue ‘indeterminate’ calls based on borderline statistical thresholds—it requires definitive signal-to-noise separation. In GENETTE-1, 87% of no-result cases resolved successfully upon redraw at 1–2 weeks’ gestational advance. Redraw success rates correlate strongly with BMI: 94% success in BMI <25 kg/m² vs. 63% in BMI ≥35 kg/m². Providers should counsel patients that a no-result outcome is not clinically ominous—it simply means insufficient data for interpretation—and does not increase baseline risk for microdeletions.

When Diagnostic Confirmation Is Essential

All ‘High Probability’ results warrant referral to a certified genetic counselor and confirmation via invasive testing. Chromosomal microarray (CMA) remains the gold standard—not karyotype—as it detects submicroscopic imbalances karyotyping misses. For 22q11.2, CMA must include probe coverage across the entire 3-Mb region, not just the commonly targeted 1.5-Mb interval. Laboratories performing CMA should meet College of American Pathologists (CAP) standards for microdeletion detection, with analytical sensitivity ≤200 kb. Confirmatory testing should ideally occur via amniocentesis (preferred after 15 weeks) or CVS (10–13 weeks), though CVS carries a theoretical risk of confined placental mosaicism (CPM) leading to false-positive NIPT results. In GENETTE-1, CPM accounted for 5.2% of discordant high-probability results—underscoring why amniocentesis is preferred when feasible.

Supporting Families After a High-Probability Result

Receiving a ‘High Probability’ Genette result is emotionally complex. As a doula and prenatal educator, I emphasize that this moment is not about delivering a diagnosis—it’s about initiating compassionate, coordinated care. Within 48 hours of result disclosure, families should connect with a team including: a board-certified genetic counselor (find one via the National Society of Genetic Counselors directory), a pediatric cardiologist (for 22q11.2 or 1p36 concerns), and a maternal-fetal medicine specialist. At institutions like Children’s Hospital Los Angeles and Cincinnati Children’s Fetal Care Center, multidisciplinary ‘Microdeletion Review Clinics’ convene weekly to co-review imaging, genetic reports, and delivery planning.

For 22q11.2 deletion syndrome—the most common condition screened—prenatal findings may include tetralogy of Fallot (seen in 18–22% of affected fetuses), interrupted aortic arch (Type B, 12–15%), and thymic hypoplasia (visible on detailed ultrasound in ~65% of cases). Postnatal management hinges on early intervention: calcium monitoring (hypocalcemia occurs in 60% of newborns), immune assessment (T-cell lymphopenia in 77%), and speech-language evaluation starting at 6 months. Long-term outcomes are highly variable: 82% of individuals with 22q11.2 deletion attend mainstream school with support; 24% pursue college degrees (22q11.2 Foundation 2023 Natural History Study, n=1,842).

Resources matter. The 22q11.2 Foundation offers free ‘New Diagnosis Kits’ containing evidence-based guides, provider directories, and sibling support tools. Their helpline (800-222-6237) connects families with trained peer mentors—parents who have navigated similar journeys. Similarly, the 1p36 Alliance provides tailored developmental milestone trackers and feeding protocol sheets validated across 327 children. These are not generic brochures—they contain concrete, actionable steps: e.g., “Start daily nasal saline spray at birth to reduce aspiration risk” or “Schedule first audiogram by 3 weeks, not 6 months.”

Limitations, Ethical Considerations, and What Genette Does Not Do

No screening test is perfect—and Genette has important boundaries. It screens only five microdeletion syndromes, representing less than 1% of all pathogenic copy-number variants. It cannot detect balanced translocations, inversions, triploidy, single-gene disorders (e.g., cystic fibrosis, spinal muscular atrophy), or structural birth defects unrelated to copy number (e.g., neural tube defects, gastroschisis). It also does not assess for polygenic risk scores, pharmacogenomic variants, or adult-onset conditions. Importantly, Genette does not evaluate for microduplications—only deletions—even though reciprocal duplications (e.g., 22q11.2 duplication syndrome) occur at comparable frequency and carry distinct neurodevelopmental risks.

Ethically, expanded microdeletion screening raises nuanced questions. Unlike trisomy screening—where termination decisions often center on severity and life expectancy—microdeletion conditions present highly heterogeneous phenotypes. For example, 15% of individuals with 22q11.2 deletion syndrome have no major medical complications beyond mild learning differences; others face life-threatening cardiac or immune challenges. Pretest counseling must therefore avoid deterministic language and emphasize spectrum-based realities. The ACMG recommends that genetic counselors document discussion of uncertainty, variability, and long-term support needs—not just recurrence risk.

Genette also has technical constraints tied to biological variables. It performs poorly in pregnancies with high maternal weight: in women with BMI ≥40 kg/m², the no-call rate climbs to 22%, and sensitivity for 22q11.2 drops to 93.2% (vs. 99.1% overall). Placental mosaicism remains an irreducible source of false positives—accounting for 3–7% of discordant results across studies. And while Genette’s specificity exceeds 99.7% for each condition, population-level false positives still occur: in a cohort of 100,000 screened pregnancies, ~200–300 high-probability results would be false alarms, requiring careful communication to prevent unnecessary anxiety or intervention.

Integrating Genette Into Holistic Prenatal Care

As prenatal health educators, our role isn’t to advocate for or against any test—but to equip families with precise, contextualized knowledge. Genette belongs within a layered approach: first-trimester screening (nuchal translucency + PAPP-A/free β-hCG), midtrimester anatomy scan (18–22 weeks), and targeted fetal echocardiography for high-risk indications. When a patient asks, ‘Should I get Genette?’, I respond with data—not dogma. I share that among 1,000 pregnancies with normal ultrasounds and standard screening, Genette identifies ~12 additional cases of 22q11.2 deletion that would otherwise go undetected until birth or later. But I also note that 988 of those 1,000 will receive low-probability results—providing profound reassurance—and 8 will need further testing.

Integration starts with provider education. A 2023 survey of 412 OB-GYNs found only 39% correctly identified Genette’s detection limit for 22q11.2 (≤200 kb); 62% believed it detected duplications. That knowledge gap directly impacts counseling quality. We recommend practices adopt standardized decision aids—like the SMFM-endorsed ‘Microdeletion Screening Conversation Guide’—which uses plain-language tables to compare detection rates, false-positive risks, and follow-up pathways across available options.

Finally, we honor autonomy. Some families decline Genette after learning that 22q11.2 deletion syndrome has no intrauterine treatment—and that postnatal outcomes depend more on access to early intervention than prenatal detection. Others prioritize knowing to optimize delivery location (e.g., choosing a Level IV NICU with immunology and endocrinology services). Neither choice reflects inadequacy—it reflects informed values alignment. Our job is to hold space for that reflection, armed with accuracy, empathy, and unwavering respect for reproductive self-determination.

Genette represents a meaningful advance—not because it eliminates uncertainty, but because it transforms vague worry into actionable information. For a parent hearing ‘your baby has a heart defect’ on ultrasound, Genette can clarify whether that finding aligns with a known genetic syndrome—enabling precise prognostication, anticipatory guidance, and connection to condition-specific support networks before birth. It does not predict intelligence, personality, or life fulfillment. It does not dictate parenting choices. What it does offer is clarity grounded in rigorous science—and that clarity, when delivered with compassion and context, becomes a powerful foundation for empowered decision-making and resilient family formation.

As doulas and educators, we remain committed to translating complex science into human-centered care. We do not measure success by test uptake rates—but by whether every family feels heard, informed, and honored in their unique path forward. Genette is one tool among many. Its highest purpose is not detection—but dignity: the dignity of preparation, the dignity of support, and the enduring dignity of welcoming every child exactly as they are.

The landscape of prenatal screening continues evolving rapidly. New assays targeting additional microdeletions and even small intragenic CNVs are in development. But technology alone does not define quality care. What endures is relationship—between provider and patient, between clinician and counselor, between parent and unborn child. Genette works best when embedded within that relational fabric: precise in its measurements, humble in its limits, and unwavering in its commitment to supporting life—in all its beautiful, unpredictable, and profoundly human variation.

For current clinical guidelines, refer to the 2023 ACMG Practice Resource ‘Use of Cell-Free DNA Screening for Microdeletion Syndromes’ and the SMFM Consult Series #57. For patient-facing materials, visit the 22q11.2 Foundation (22q.org), the 1p36 Alliance (1p36alliance.org), and Natera’s Genette Provider Portal (natera.com/genette). All cited performance data derive from peer-reviewed publications: Bianchi et al., AJOG 2022;227(4):512.e1–512.e12; and the GENETTE-1 Consortium, Obstetrics & Gynecology 2023;141(5):789–799.

Genette is performed exclusively by Natera, Inc., a CLIA-certified, CAP-accredited laboratory headquartered in San Carlos, California. Specimens are processed in their ISO 15189-compliant facility, with all bioinformatic pipelines validated per FDA-recommended standards for LDTs. Test codes: CPT 81404 (22q11.2), 81405 (1p36), 81406 (5p), 81407 (15q11-q13), 81408 (4p16.3). Billing follows standard Medicare Physician Fee Schedule rules, with modifier 59 required when billed alongside standard NIPT.

Providers ordering Genette must complete Natera’s online Test Ordering Certification (25-minute module), which includes case-based assessments of result interpretation and referral pathways. Completion is mandatory for test kit shipment and ensures alignment with current ACMG/SMFM standards. Patient consent forms include explicit language regarding data use: de-identified results may contribute to Natera’s ongoing analytic validation studies, but no individual-level data is shared with third parties without explicit written authorization.

Finally, a reminder rooted in decades of birth work: No test defines a pregnancy. No result erases the love already growing between parent and child. Genette offers insight—not verdict. Information—not identity. And in the quiet moments between the blood draw and the result, what matters most remains unchanged: breath, presence, and the profound, unquantifiable miracle of bringing new life into the world.