CurrentCapital BluecrossPolicy MP 2.278

Invasive Prenatal (Fetal) Diagnostic Testing

Defines medical necessity and investigational uses of invasive prenatal genetic diagnostic tests (e.g., CMA, single-gene molecular testing, NGS, WES) for pregnancies undergoing chorionic villus sampling or amniocentesis and applies to Capital BlueCross products with benefit variations.

Policy Summary

PayerCapital Bluecross

PolicyInvasive Prenatal (Fetal) Diagnostic Testing

Policy CodePolicy MP 2.278

Change TypeAdministrative updateno material clinical changes

Effective DateDec 1, 2025

Next Review Date

Key ActionObtain and document comprehensive pretest and posttest genetic counseling and informed consent prior to ordering invasive prenatal diagnostic testing.

SourceLink

POLICY UPDATE CHANGES

No material clinical or coverage changes in this revision.

CMA MNCMA coverage

WES INVWES stance

NGS INVNGS stance

Criteria req'dSingle-gene testing

RequiredGenetic counseling

Trek Health ingests and normalizes Transparency in Coverage data and payer policy updates to give provider organizations a clear view of how commercial reimbursement behaves across markets, payers, and services. Our platform transforms raw payer disclosures into structured intelligence that supports contract evaluation, payer negotiations, and service line strategy. By combining market benchmarks with ongoing policy visibility, Trek helps teams identify variability, risk, and opportunity in commercial reimbursement. The result is faster insight, stronger negotiating positions, and more informed financial decisions.

300 kb–1 MbCNV cutoff range

Coverage Criteria and Policy Stance

Medically necessary criteria

Covered when ALL of the following are met:

CMA coverage: Chromosomal microarray testing is considered medically necessary as an alternative to karyotyping for patients undergoing invasive prenatal diagnostic testing; low-pass genome sequencing may be considered medically necessary as an alternative to CMA.

See Policy Guidelines for specifics.

Single-gene molecular testing coverage: Molecular analysis for single-gene disorders is medically necessary when the pregnancy is identified as high risk: for autosomal dominant conditions at least one parent has a known pathogenic variant; for autosomal recessive conditions both parents are suspected or known carriers or one parent is affected and the other is a carrier; for X-linked conditions a parent is suspected or known to be a carrier AND all of the following are met: the natural history of the disease is well understood with reasonably high morbidity, the disease has high penetrance, the genetic test has adequate sensitivity and specificity and residual risk is understood, and an association of the marker with the disorder has been established.

Additional conditions required for single-gene testing per policy.

Investigational services

Not covered - WES/NGS: Prenatal diagnostic whole exome sequencing (with or without trio) and the use of next-generation sequencing in invasive prenatal testing are considered investigational.

Insufficient evidence for health outcomes or benefits.

Medically necessary indications

Covered when criteria below are met

Indications for CMA or advanced testing: CMA is recommended for a fetus with one or more major structural abnormalities identified on ultrasound undergoing invasive prenatal diagnosis; in structurally normal fetuses undergoing invasive testing, either karyotype or CMA may be performed; CMA is also recommended for evaluation of intrauterine fetal death/stillbirth when cytogenetic analysis is desired.

From ACOG recommendations and policy text

Indications for prenatal sequencing (WES/WGS): Prenatal exome or genome sequencing may be considered when a fetus has a major single anomaly or multiple anomalies and prior CMA/karyotype have not yielded a diagnosis, or when there is a personal history of a prior undiagnosed affected fetus/child with recurrence and prior testing is noninformative; trio sequencing is preferred in some contexts and CMA should be run before or in parallel with prenatal exome sequencing when CNV detection is needed.

Sequencing not routine; perform after genetics consultation

Not routine / research-only

Not routinely covered / generally considered not standard

Routine WES/WGS: Routine use of whole-exome or whole-genome sequencing for prenatal diagnosis is not recommended outside clinical trials or research protocols due to limitations including turnaround time and high rates of false positives, false negatives, and variants of unknown significance.

Policy cites professional society positions and technical limitations

Chromosomal microarray (CMA) coverage

Covered when ALL of the following are met:

CMA coverage rationale: CMA testing has a higher detection rate of pathogenic chromosomal alterations than karyotyping and has the highest yield in fetuses with malformations identified by ultrasound; the American College of Obstetricians and Gynecologists recommends CMA testing in women undergoing an invasive diagnostic procedure.

Evidence sufficient to determine meaningful improvement in net health outcome

Single-gene molecular testing

Covered when ALL of the following are met:

Single-gene testing rationale: Molecular testing for single-gene disorders is supported when there is a known pathogenic familial variant and the pregnancy meets high-risk parental criteria (autosomal dominant: one parent with pathogenic variant; autosomal recessive: both parents carriers or one affected and the other a carrier; X-linked: a parent suspected or known carrier) AND the disease natural history, penetrance, test sensitivity/specificity, and marker–disorder association meet policy requirements.

Evidence supports clinical validity and potential changes in reproductive decision making

Next-generation sequencing (NGS) — investigational (not covered for invasive prenatal testing)

Not covered / Investigational when used for invasive prenatal testing:

NGS investigational: The clinical validity of next-generation sequencing in the prenatal setting is unknown; concerns exist about interpretation and clinical relevance, and evidence is insufficient to determine effects on health outcomes. When used to bill for NGS in invasive prenatal testing it is considered investigational and not covered (procedure codes such as 81470 and certain proprietary U-codes are listed as investigational).

NGS procedure codes are listed as investigational and not covered

Policy history — coding and test-type coverage actions

policy_history_actions: Policy history records: 12/02/2021 added code 81349; 10/24/2022 added low-pass sequencing as medically necessary and designated whole exome sequencing not medically necessary while codes 0335U and 0336U were designated NMN; 06/12/2024 added 0469U as NMN; 11/07/2024 updated prenatal diagnostic whole exome sequencing to investigational from NMN along with 0335U, 0336U, and 0469U; 06/10/2025 added 0567U as NMN; 06/12/2025 administrative updates removed Benefit Variations; 08/14/2025 consensus review no changes to policy statement.

Entries indicate coverage stance changes for test types and specific codes.

This evidence review does NOT cover prenatal carrier testing, preimplantation genetic diagnosis or screening, noninvasive prenatal testing, or testing in the setting of fetal demise. These exclusions reflect the scope of the policy, which focuses on invasive prenatal diagnostic methodologies (e.g., CVS, amniocentesis) and their use for diagnosing copy number variants and single‑gene disorders.

The policy does not support routine sequencing of fetal tissue obtained from invasive procedures in the absence of fetal anomalies. Routine prenatal WES/WGS is discouraged outside clinical trials; exceptional situations (for example, a strong family history without a prenatal phenotype) may be considered only after multidisciplinary expert review and preferably within a research protocol, and when performed, should generally be trio sequencing.

The use of next‑generation sequencing (NGS) in the setting of invasive prenatal testing is considered investigational. The evidence is insufficient to determine clinical validity and net health outcomes for NGS applied to fetal tissue, and NGS procedure and proprietary codes listed for this setting are identified as investigational and not covered when billed for invasive prenatal testing.

Policy history documents coverage-status changes for whole exome sequencing (WES) over time. WES has been described as having increased diagnostic yield in some fetal series (identifying abnormalities in approximately 20–30% of selected cases missed by standard testing), but policy updates have moved WES through designations including Not Medically Necessary and, more recently, to an investigational stance for prenatal diagnostic use. See the Policy History entries for dated coding and status actions.

If the criteria for single‑gene molecular analysis are not met (for example, absence of a known familial pathogenic variant and the other required clinical conditions), invasive diagnostic prenatal molecular testing is considered investigational and may be denied. The policy states there is insufficient evidence to support favorable health outcomes when single‑gene testing criteria are unmet.

Whole exome sequencing (WES) and whole genome sequencing (WGS) are not supported routinely for prenatal diagnosis and should not be performed simply at parental request without qualifying clinical indications. Professional guidance and the policy emphasize reserving WES/WGS for selected cases—e.g., fetuses with major anomalies after CMA/karyotype are noninformative—and typically after genetics consultation.

The rationale for not supporting NGS (including WES/WGS) in invasive prenatal testing is that the clinical validity is unknown in the prenatal setting and there are significant concerns about interpretation, high rates of variants of uncertain significance, false positives and negatives, and uncertain impact on health outcomes. The evidence is therefore insufficient to determine effects on clinical management and net health outcomes for routine use in this context.

Policy history shows that specific proprietary and miscellaneous procedure codes have at times been designated Not Medically Necessary or otherwise updated. Examples called out in historical entries include 0335U, 0336U, 0469U, 0567U; providers should review coding history and current policy coding tables when submitting claims.

Indications Supported for Testing

CMA recommended for fetus with one or more major structural abnormalities on ultrasound

CMA for fetal structural abnormality: Fetus with one or more major structural abnormalities on ultrasound undergoing invasive prenatal diagnosis — CMA is recommended.

CMA typically can replace the need for fetal karyotype.

High-risk pregnancy for single-gene disorder when parental/variant criteria met

High-risk pregnancy for single-gene disorder: Pregnancy identified as high risk for a single-gene disorder when parental variant/carrier criteria are met: autosomal dominant—at least one parent has a known pathogenic variant; autosomal recessive—both parents are suspected or known carriers or one parent is affected and the other a carrier; X-linked—a parent is suspected or known carrier AND all additional disease/test conditions are satisfied (well-understood natural history, high penetrance, adequate test sensitivity/specificity, and established marker–disorder association).

Family-specific mutation should usually be identified in an affected relative or carrier parent prior to offering prenatal molecular diagnosis.

Eligibility and Pre-test Requirements

When prenatal molecular diagnosis is intended for a known single‑gene disorder, the policy expects a family‑specific pathogenic variant to be identified in an affected relative or a carrier parent before offering prenatal testing. This requirement supports high clinical validity for targeted testing and helps limit uncertain results. Providers should document identification of the familial variant when available.

In most circumstances, the family‑specific mutation should be identified prior to prenatal molecular diagnosis—ideally in an affected relative or a carrier parent. If a proband sample is unavailable, parental sequencing may be considered (for example, to assess shared carrier status), but targeted testing directed at a known familial variant is preferred.

Eligibility for prenatal molecular testing depends on established clinical criteria (see policy criteria sets). Key prerequisites include a qualifying clinical indication (e.g., fetus with major anomaly or a high‑risk pregnancy for a known single‑gene disorder), documentation of family‑specific pathogenic variant when applicable, and performance of prior recommended testing such as CMA or karyotype where indicated. Specific node logic and detailed criteria are provided in the full policy criteria sections.

Additional eligibility considerations reference the strength of evidence and clinical utility: molecular testing for single‑gene disorders is supported when there is a well‑understood natural history, high penetrance, and reliable test sensitivity and specificity—conditions that are most often met when a familial pathogenic variant is known. The summary of evidence and policy criteria outline these expectations.

For single‑gene disorders, the policy generally requires identification of the family‑specific pathogenic variant before prenatal testing is offered. This requirement minimizes uncertainty and enables high analytic and clinical validity of targeted prenatal molecular assays. Where prior testing of an affected proband is not possible, parental testing strategies may be considered per the policy guidance.

Provider Responsibilities and Prior Authorization

Prior Authorization

Prior Authorization Required (product-specific)

Some products and benefit programs administered by Capital BlueCross require product-specific prior authorization for invasive prenatal molecular testing. Confirm member benefits and any program-specific prior authorization requirements before ordering or submitting claims to avoid denial or delay.

Verify member-specific benefit coverage and any product or program prior authorization requirements prior to testing
FEP and other programs may follow alternative policy manuals or benefit rules — confirm applicable program guidance

Prior Authorization

Prior Authorization Expectation for WES/WGS

Whole-exome and whole-genome sequencing (WES/WGS) in the prenatal setting is generally reserved for selected fetal cases (for example, a fetus with major anomalies where CMA and targeted testing have failed to yield a diagnosis) and is not a routine first-line test. Prior authorization or case review may be expected when WES/WGS is requested for prenatal diagnosis.

WES/WGS: reserved for select fetal cases after CMA and other targeted testing have been performed or deemed insufficient

Coding, Billing, and Laboratory Notes

Laboratory/billing notesmixed

No codes listed

Investigational Procedure Codes (NGS)CPTNot Covered

81470

Procedure code listed as used to bill for next-generation sequencing in the setting of invasive prenatal testing — considered Investigational; therefore, not covered

Investigational HCPCS / Proprietary CodesHCPCSNot Covered

0335U	Investigational, therefore not covered
0336U	Investigational, therefore not covered
0469U	Investigational, therefore not covered

Covered when medically necessary — Procedure CodesCPTCovered

81228	Covered when medically necessary
81229	Covered when medically necessary
81349	Covered when medically necessary
81405	Covered when medically necessary
0567U	Covered when medically necessary

Relevant ICD-10 Diagnosis Codes listedICD-10

O09.891	Supervision of other high-risk pregnancies, first trimester
O09.892	Supervision of other high-risk pregnancies, second trimester
O09.893	Supervision of other high-risk pregnancies, third trimester
O28.5	Abnormal chromosomal and genetic finding on antenatal screening of mother
O35.02X0	Maternal care for (suspected) central nervous system malformation or damage in fetus, anencephaly, not applicable or unspecified
O35.02X1	Maternal care for (suspected) central nervous system malformation or damage in fetus, anencephaly, fetus 1
O35.10X0	Maternal care for (suspected) chromosomal abnormality in fetus, unspecified, not applicable, or unspecified
O35.11X0	Maternal care for (suspected) chromosomal abnormality in fetus, Trisomy 13, not applicable or unspecified
O35.12X0	Maternal care for (suspected) chromosomal abnormality in fetus, Trisomy 18, not applicable or unspecified
O35.13X0	Maternal care for (suspected) chromosomal abnormality in fetus, Trisomy 21, not applicable or unspecified

1–10 of 18

1/2

Referenced ICD-10 O35 series (fetal anomaly maternal care)ICD-10

O35.AXX2	Maternal care for other (suspected) fetal abnormality and damage, fetal facial anomalies, fetus 2
O35.AXX3	Maternal care for other (suspected) fetal abnormality and damage, fetal facial anomalies, fetus 3
O35.AXX4	Maternal care for other (suspected) fetal abnormality and damage, fetal facial anomalies, fetus 4
O35.AXX5	Maternal care for other (suspected) fetal abnormality and damage, fetal facial anomalies, fetus 5
O35.AXX9	Maternal care for other (suspected) fetal abnormality and damage, fetal facial anomalies, other fetus
O35.BXX0	Maternal care for other (suspected) fetal abnormality and damage, fetal cardiac anomalies, not applicable or unspecified
O35.BXX1	Maternal care for other (suspected) fetal abnormality and damage, fetal cardiac anomalies, fetus 1
O35.BXX2	Maternal care for other (suspected) fetal abnormality and damage, fetal cardiac anomalies, fetus 2
O35.BXX3	Maternal care for other (suspected) fetal abnormality and damage, fetal cardiac anomalies, fetus 3
O35.BXX4	Maternal care for other (suspected) fetal abnormality and damage, fetal cardiac anomalies, fetus 4

1–10 of 40

1/4

Procedure / Proprietary / molecular codes referenced in policy historymixed

0335U	Proprietary/procedure code (listed in policy history)
0336U	Proprietary/procedure code (listed in policy history)
0469U	Proprietary/procedure code (added as NMN 06/12/2024)
0567U	Proprietary/procedure code (added as NMN 06/10/2025)
81349	Molecular pathology code (added 12/02/2021)

Laboratory CNV size cutoff (typical lab thresholds)

Typical laboratory CNV size cutoffLaboratory-established size cutoffs for CNVs not previously reported typically range from 300 kb to 1 Mb

Purpose of cutoffSize cutoffs help distinguish potentially pathogenic CNVs from benign polymorphic CNVs

Confirmatory testingCNVs of appropriate size are often confirmed by an orthogonal method (e.g., FISH, MLPA, PCR)

Parental studiesParental testing is indicated for CNVs of appropriate size to assess inheritance and pathogenicity

Exome proportion of known disease-causing variants (~85%)

Services Considered Not Covered / Investigational

Whole exome sequencing and next‑generation sequencing for invasive prenatal testing are considered investigational and not covered. The summary of evidence states that while CMA and targeted single‑gene testing have sufficient evidence of clinical utility, the evidence for NGS approaches in the prenatal invasive setting is lacking, and interpretation and clinical relevance remain concerns.

Routine prenatal sequencing (WES/WGS) of fetal tissue without fetal anomalies is not supported. Professional statements and the policy indicate sequencing should be reserved for fetuses with major anomalies or strong family history and should follow or be concurrent with CMA/karyotype when CNV detection is needed. Routine sequencing solely by parental request is discouraged.

Next‑generation sequencing used to bill invasive prenatal testing is listed as investigational and not covered; the policy identifies specific investigational codes (for example, 81470 and proprietary codes 0335U, 0336U, 0469U) that have been associated with investigational/not‑covered designations when used in this setting. Providers should confirm current coding and coverage before billing.

Historical coding actions are documented in the policy history: additions and status changes include adding code 81349 (12/02/2021), adding proprietary codes 0335U and 0336U (10/01/2022), designation of low‑pass sequencing as medically necessary and WES as Not Medically Necessary (10/24/2022), later changes to investigational status for prenatal WES and associated U‑codes (11/07/2024), and subsequent administrative updates (including addition of 0469U and 0567U). These entries reflect evolving policy and coding positions.

Background and Definitions

Invasive prenatal testing (e.g., CVS or amniocentesis) obtains fetal tissue to diagnose chromosomal abnormalities, copy number variants, and single‑gene disorders to inform pregnancy management. Chromosomal microarray (CMA) identifies submicroscopic CNVs not seen on karyotype and has the highest diagnostic yield in fetuses with ultrasound‑identified malformations; CMA is recommended by ACOG for patients undergoing invasive diagnostic procedures.

Definition — Invasive prenatal testing (CVS or amniocentesis)

DefinitionInvasive prenatal testing refers to direct testing of fetal tissue, typically by chorionic villus sampling (CVS) or amniocentesis, for genetic diagnostic purposes

PurposeUsed to diagnose chromosomal abnormalities, CNVs, and single-gene disorders to inform pregnancy management

Common proceduresIncludes obtaining fetal tissue for karyotyping, FISH, CMA, PCR, NGS, and MLPA

Definition — Chromosomal microarray (CMA)

Definition

Policy Summary

PayerCapital Bluecross

PolicyInvasive Prenatal (Fetal) Diagnostic Testing

Policy CodePolicy MP 2.278

Change TypeAdministrative updateno material clinical changes

Effective DateDec 1, 2025

Next Review Date

Key ActionObtain and document comprehensive pretest and posttest genetic counseling and informed consent prior to ordering invasive prenatal diagnostic testing.

SourceLink

On This Page

Covered situations including major structural abnormalities, recurrent/previously affected fetus/child, stillbirth evaluation when cytogenetics desired

Covered situations including major structural abnormalities, recurrent/previously affected fetus/child, stillbirth evaluation when cytogenetics desired: Covered indications include: fetus with one or more major structural abnormalities on ultrasound; recurrent or prior undiagnosed affected fetus or child with similar anomalies where prior testing was noninformative; and stillbirth/intrauterine fetal death evaluation when cytogenetic analysis is desired. In structurally normal fetuses undergoing invasive testing, either karyotype or CMA may be performed.

Parental or proband testing may be needed for interpretation of variants.

Fetuses undergoing invasive diagnostic prenatal testing (amniocentesis or CVS) especially with malformations or known familial pathogenic variant — CMA and single-gene testing supported; ICD-10 codes referenced

Fetuses undergoing invasive diagnostic prenatal testing (amniocentesis or CVS): Fetuses undergoing invasive diagnostic prenatal testing (amniocentesis or chorionic villus sampling), especially when fetal malformations are identified on ultrasound or when a familial pathogenic variant is known, are appropriate candidates for CMA and for single-gene molecular testing when familial variants are available. Relevant ICD-10 O35 maternal care diagnosis codes are referenced for such indications.

CMA and single-gene testing supported; specific ICD-10 codes listed in coding section.

Evaluation of suspected fetal anomalies across organ systems detected prenatally

Evaluation of suspected fetal anomalies across organ systems: Evaluation of suspected fetal anomalies detected prenatally across organ systems (facial, cardiac, genitourinary, musculoskeletal, upper and lower extremities) is included among covered indications for invasive prenatal diagnostic testing with CMA or other appropriate testing.

Multiple O35 ICD-10 codes reference specific fetal anomaly categories.

Laboratory and testing expectations include performance in appropriate, accredited settings: testing should be performed in an FDA‑cleared/approved test or in a CLIA‑certified laboratory, with laboratory‑developed tests carried out in CLIA‑licensed high‑complexity labs. Laboratories are expected to follow applicable variant classification and reporting standards. Documentation of laboratory credentials may be required for authorization or claims review.

The policy notes that many commercial and academic laboratories offer CMA, single‑gene testing, and related services, but also emphasizes that tests used for clinical prenatal diagnosis should meet regulatory and quality expectations (FDA clearance or CLIA certification). Parental or reflex testing strategies are described to help interpret CNVs or VUS findings.

Trio testing (fetus + parents) increases diagnostic yield and may be requested/documented

Billing Rule

Code-level Coverage and Prior Authorization Note

Codes associated with next-generation sequencing (NGS) billed in the setting of invasive prenatal testing may be designated investigational or not medically necessary; this can affect coverage and prior authorization. Confirm current code-level coverage and prior authorization expectations before submission.

The presence of a code in the coding section does not guarantee coverage — benefit terms control
Confirm whether prior authorization is required for the specific procedure code being billed

Billing Rule

Confirm Coverage / Prior Auth for Specific Procedure Codes

Confirm coverage and prior authorization for specific procedure codes prior to testing. Some codes used for NGS in invasive prenatal testing have historically changed status (covered, not covered, NMN, investigational).

Codes historically listed as investigational or NMN include 0335U, 0336U, 0469U, 0567U — verify current status for the member and effective dates
Covered/medically necessary codes may include 81228, 81229, 81349, 81405, 0567U (when indicated) — confirm member benefits

Denial Risk

Investigational When Criteria Unmet

If the criteria for molecular analysis of a single-gene disorder are not met, invasive diagnostic prenatal (fetal) testing is considered investigational and is not covered.

Do not bill invasive prenatal molecular tests as medically necessary when single-gene criteria are unmet; such services may be denied as investigational

Documentation Required

Laboratory Certification and Regulatory Expectations

Laboratory testing must be performed in a CLIA-certified laboratory for high-complexity testing or be FDA-cleared/approved when applicable. Laboratory-developed tests (LDTs) must meet CLIA requirements. Non-CLIA or non-FDA‑cleared testing may be considered noncompliant and subject to denial.

Ensure the performing laboratory is CLIA-certified for high-complexity testing
Prefer FDA-cleared/approved tests when available; LDTs must still be CLIA-compliant

Denial Risk

NGS Investigational — Denial Risk

When next-generation sequencing is billed for invasive prenatal testing, there is an increased denial risk because NGS-based prenatal testing has been designated investigational or not medically necessary in some contexts. Review the policy coding and medical necessity criteria before ordering or billing.

NGS billed for invasive prenatal testing may be considered investigational — potential for denial
Confirm clinical indication aligns with policy criteria (e.g., fetal anomalies after CMA) before proceeding

Billing Rule

Coding-based Denial Risk

Some codes have changed status over time (e.g., 0335U, 0336U, 0469U, 0567U). Coding-based denials can occur if outdated code status is assumed. Always verify the current effective status of these codes for the member and date of service.

0335U, 0336U, 0469U: previously designated NMN or investigational; status updated at different dates — confirm current designation
0567U added as NMN effective 07/01/2025 per policy history

Documentation Required

Genetic Counseling and Informed Consent Documentation

Comprehensive pretest and posttest genetic counseling must be documented. Counseling should be provided by a clinician with genetics expertise and should include discussion of benefits, limitations, potential results (including variants of uncertain significance), risks such as nonpaternity or adult-onset findings, and implications for family members. Informed consent must be obtained and documented before ordering testing.

Document pretest and posttest genetic counseling by a genetics‑experienced provider
Document informed consent discussions covering possible uncertain results, incidental findings, nonpaternity, and adult-onset disease

Documentation Required

Laboratory and Regulatory Documentation

Testing should be ordered in accordance with regulatory expectations: use FDA-cleared tests when available or CLIA-certified laboratory-developed tests (LDTs) for high-complexity testing. Maintain documentation of laboratory certifications and test validation as part of the medical record.

Document CLIA certification or FDA clearance for the laboratory/test used
Retain test reports and validation documentation in the medical record

Step Therapy

Stepwise Testing Preference: CMA Before or With Prenatal Exome Sequencing

When copy-number variant (CNV) detection is needed (for example, to evaluate structural fetal anomalies), chromosomal microarray analysis (CMA) should be performed before or in parallel with prenatal exome sequencing because prenatal exome sequencing is not validated to detect all CNVs.

Order CMA prior to or in parallel with prenatal exome sequencing when CNV detection is clinically indicated
Consider low-pass genome sequencing as an alternative to CMA where supported by benefit coverage

Proportion in exomeApproximately 85% of known disease-causing variants occur within the exome (protein-coding regions)

Implication for WESWES captures the majority of protein-coding regions and is a cost-effective method to detect many pathogenic variants

LimitationsDespite high exome coverage of known variants, WES has concerns including technical complexity, coverage gaps, bioinformatics, and VUSs

None stated (placeholder key/value)

None statedNo additional thresholds or values stated in the policy excerpt

ContextPlaceholder entry — no supporting policy text provided for this item

ActionNo action required; retain for reference if thresholds are later specified

Chromosomal microarray (CMA) measures genome-wide gains and losses of DNA to identify aneuploidy, structural chromosomal changes, and submicroscopic abnormalities (CNVs)

Clinical roleCMA has improved resolution over karyotyping and can replace karyotype in many invasive prenatal diagnostic contexts

LimitationsCMA cannot detect balanced rearrangements or sequence inversions and can increase detection of variants of uncertain significance (VUS)

CMA abbreviation definition — chromosomal microarray analysis

AbbreviationCMA = chromosomal microarray analysis

Alternate termsAlso referred to as array comparative genomic hybridization (aCGH) or oligo/SNV arrays depending on platform

FunctionDetects copy number variants (CNVs) by comparing patient DNA to reference sequences

WES / WGS definition — whole exome and whole genome sequencing brief

DefinitionWhole exome sequencing (WES) examines the protein-coding regions of the genome to identify single-nucleotide variants and small indels; whole genome sequencing (WGS) assesses the entire genome

Clinical contextWES may identify diagnoses missed by standard testing in some fetal series (reported additional diagnostic yield ~20–30%) but is not recommended routinely outside trials

Trio testingTrio (fetus plus both parents) sequencing increases diagnostic yield and is preferred in some contexts

CNV / SNV arrays definitions

CNV arraysCNV detection is performed by CMA platforms (oligo or SNV arrays) that identify gains and losses of DNA segments

SNV arraysSNV arrays also provide genome-wide copy number analysis and can detect triploidy and uniparental disomy in addition to CNVs

Methods referencedArrays detect CNVs by comparing fluorescence intensity of patient and reference DNA; platforms vary in probe density and design

Amniocentesis definition (timing 15–20 weeks)

DefinitionAmniocentesis is a procedure that removes a small amount of amniotic fluid for fetal genetic testing; traditional amniocentesis is usually performed between 15 and 20 weeks of gestation

SpecimensAmniotic fluid can be used for genetic testing or measurement of biochemical markers

IndicationTypically performed when a fetus is identified as being at increased risk for chromosomal abnormality or single-gene disorder

Chorionic villus sampling (CVS) definition (after 9 weeks)

DefinitionChorionic villus sampling (CVS) involves obtaining chorionic villi of fetal origin via transcervical or transabdominal access to the placenta

TimingCVS is generally performed after 9 weeks of gestation

NoteChorionic villi are vascular processes of fetal origin used for genetic testing

Karyotyping definition

DefinitionKaryotyping is the examination of chromosomes from cells (e.g., amniotic fluid or CVS) to count chromosomes and detect large structural changes

DetectsKaryotype can identify aneuploidy and large structural chromosomal abnormalities but has lower resolution than CMA

RoleMay be performed alternatively or in conjunction with CMA depending on clinical context

Low-pass genome sequencing — alternative to CMA definition

DefinitionLow-pass genome sequencing is a sequencing approach validated as an alternative to chromosomal microarray for detection of copy number variants in prenatal diagnosis

EvidencePublished validation studies (e.g., Chaubey et al.; Kocheva et al.) support low-pass sequencing utility in CNV detection

Policy stanceLow-pass genome sequencing may be considered medically necessary as an alternative to CMA in invasive prenatal testing

Whole exome sequencing (WES) — definition and policy history reference

DefinitionWhole exome sequencing (WES) is a genome-scale sequencing approach that examines coding regions; it can detect many single-gene pathogenic variants relevant to prenatal diagnosis

Policy historyPolicy history notes WES has had changing coverage designations (e.g., previously Not Medically Necessary and later designated investigational for prenatal diagnostic WES in updates) — see policy history entries

Clinical recommendationACMG recommends considering WES when targeted tests have failed to determine a diagnosis in a fetus with multiple congenital anomalies; routine prenatal WES/WGS is not recommended outside clinical trials