Fetal Fibronectin, Inflammatory Biomarkers, and Salivary Hormone Testing for Preterm Labor — CPB 0166 | AETNA Coverage Update

Aetna modified CPB 0166 covering fetal fibronectin and related preterm labor testing, effective September 26, 2025. Here's what billing teams need to know.

Aetna, a CVS Health company, updated CPB 0166 — the Aetna fetal fibronectin coverage policy governing preterm labor risk testing. The policy covers CPT 82731 for the fetal fibronectin (fFN) immunoassay when strict medical necessity criteria are met, and explicitly excludes a long list of metabolomic, inflammatory, and salivary hormone tests. If your OB or MFM practice bills for preterm labor workups, this policy directly affects your reimbursement and your claim denial exposure.

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Quick-Reference Table

Field	Detail Copy
Payer	Aetna, a CVS Health company
Policy	Fetal Fibronectin, Inflammatory Biomarkers, and Salivary Hormone Testing for Preterm Labor
Policy Code	CPB 0166
Change Type	Modified
Effective Date	September 26, 2025
Impact Level	High
Specialties Affected	Obstetrics, Maternal-Fetal Medicine, Clinical Laboratory
Key Action	Audit your preterm labor test orders against CPT 82731 criteria; flag any claims using excluded metabolomic or salivary hormone codes before September 26, 2025

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Aetna Fetal Fibronectin Coverage Criteria and Medical Necessity Requirements 2025

The CPB 0166 Aetna system draws a hard line here: one test is covered, and nearly everything else in the preterm labor biomarker space is not.

CPT 82731 — the fetal fibronectin cervicovaginal immunoassay — is medically necessary for symptomatic pregnant women at high risk for preterm delivery. Aetna bases this on specific selection criteria described in the policy's background section, so your documentation must establish both symptom status and risk level.

Repeat fFN testing with CPT 82731 is also medically necessary, but only when the patient remains symptomatic at least two weeks after a previous negative result. If the gap between tests is less than two weeks, or if the prior result was positive, you have a much harder case to make on medical necessity. Get that clinical documentation tight before billing a repeat test.

There's no mention of prior authorization as a specific requirement in this policy update, but Aetna's coverage policy language on medical necessity criteria is detailed enough that you should treat documentation like a prior auth request — thorough, specific, and tied to the exact criteria. If your practice has a high volume of fFN claims, talk to your compliance officer about whether your current documentation templates meet the bar.

Reimbursement for CPT 82731 flows only when those criteria are satisfied. Anything else — the metabolomic panels, inflammatory biomarkers, salivary hormone tests — is not covered under this policy.

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Aetna Preterm Labor Testing Exclusions and Non-Covered Indications

This is where CPB 0166 gets expensive for practices that aren't paying attention.

Aetna considers a broad set of preterm labor biomarkers experimental, investigational, or unproven. That includes HCPCS S3652 — the salivary progesterone test specifically used to assess preterm labor risk. S3652 is listed under "HCPCS codes not covered if selection criteria are met," which is a firm non-coverage designation, not a gray area.

The metabolomic and inflammatory biomarker group is equally clear. CPT codes 0066U, 0247U, 81291, 81401, 82085, 82103, 82131, 82542, 82677, 82728, 83006, 83516, 83518, 83519, 83520, 84112, 84144, 84145, 84210, 84466, 84550, 85415, 86140, 86141, and 88324 are all in the non-covered group. That's a long list, and some of those codes — like 86140 and 86141 for C-reactive protein, or 84145 for procalcitonin — show up in other clinical contexts where they are covered. Context matters. When they're billed in connection with preterm labor risk assessment, Aetna considers them not covered under this policy.

The real issue here is that laboratories and ordering physicians may be running these panels routinely, not realizing Aetna has drawn a clear line. If your lab bills piecemeal for components of a preterm labor risk panel, audit those claims now.

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Coverage Indications at a Glance

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Aetna Fetal Fibronectin Billing Guidelines and Action Items 2025

The effective date is September 26, 2025. Use that as your deadline for each of these steps.

Copy Action Items

If you're not sure how this applies to your patient mix or your lab's panel structure, loop in your compliance officer before September 26, 2025. The non-covered list in CPB 0166 is long and specific enough that a manual audit beats a batch of denials.

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CPT, HCPCS, and ICD-10 Codes for Fetal Fibronectin and Preterm Labor Testing Under CPB 0166

Covered CPT Codes (When Selection Criteria Are Met)

Code	Type	Description Copy
82731	CPT	Fetal fibronectin, cervicovaginal secretions, semi-quantitative (not covered following cerclage insertion)

Other CPT Codes Related to CPB 0166

Code	Type	Description Copy
59320	CPT	Cerclage of cervix during pregnancy; vaginal
76815	CPT	Ultrasound, pregnant uterus, real time with image documentation, limited
84560	CPT	Uric acid; other source

Not Covered CPT Codes — Metabolomic Biomarkers and Inflammatory Markers

Not Covered HCPCS Codes

Code	Type	Description	Reason Copy
S3652	HCPCS	Saliva test, hormone level; to assess preterm labor risk	Explicitly not covered under CPB 0166

Key ICD-10-CM Diagnosis Codes

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