Introduction
Insurance claim denials are a common challenge for obstetrics practices, affecting both revenue and patient satisfaction. Because maternity care takes place over several months and includes many services, billing can be complicated. Obstetrics practices often face denial rates between 10–15%, mostly due to the extended nature of care, differences in insurance plans, and complex billing rules. These denials can delay payments, increase paperwork, and lead to confusion or frustration for patients when they receive unexpected bills.
This blog breaks down the ten most common denial codes in obstetrics, explains why they happen, and offers practical steps to help reduce them. With the right approach, practices can improve their claim approval rates, cut down on administrative work, and get paid accurately for the care they provide.
Common Denial Codes in Obstetrics
| Denial Code | Description |
|---|---|
CO 97 | The benefit for this service is included in the payment/allowance for another service. |
CO 15 | The authorization number is missing, invalid, or does not apply to the billed services |
CO 11 | The diagnosis is inconsistent with the procedure |
CO 50 | These services are non-covered because this is not deemed a medical necessity |
CO 16 | Claim/service lacks information or has submission/billing error |
CO 27 | Expenses incurred after coverage terminated |
CO 22 | This care may be covered by another payer per coordination of benefits |
CO 29 | The time limit for filing has expired |
CO 236 | This procedure or procedure/modifier combination is not compatible with another procedure |
CO 204 | This service/equipment/drug is not covered under the patient’s current benefit plan |
Detailed Analysis of Top 10 Denials
1. Denial Code: CO 97
Description: Global Package Billing Issues
Global package billing denials happen when services that should be included in the obstetric global package are billed separately, or when services that should be billed separately are denied as part of the package. The global package usually includes standard prenatal visits (about 13 for a typical pregnancy), the delivery, and postpartum care. These denials often result from billing routine care outside the global code, using the wrong modifiers for partial services, or failing to clearly document services like high-risk monitoring as separate from regular care.
Prevention:
- Clearly understand what’s included in the global OB package for each payer
- Create a comprehensive reference guide for services included vs. excluded from global packages
- Properly use modifiers for partial services (e.g., -52 for reduced services when patient transfers care)
- Document clear start and end dates for the global period
- Implement proper coding for antepartum-only care (59425-59426) when appropriate
2. Denial Code: CO 15
Description: Authorization/Precertification Issues
Authorization denials happen when required approval for a service wasn’t obtained, or when the approval doesn’t match what was actually done. While routine prenatal visits usually don’t need pre-approval, many insurance plans require it for things like genetic tests, extra ultrasounds, fetal monitoring, cerclage procedures, or hospital stays related to pregnancy complications. These denials are especially difficult in obstetrics because many of these services need to happen quickly and can’t be delayed.
Prevention:
- Verify insurance requirements for authorization at the initial OB visit
- Create a comprehensive list of which obstetric services typically require authorization by payer
- Implement an authorization tracking system specific to maternity care
- Train staff on payer-specific requirements for high-risk pregnancy services
- Develop dedicated protocols for handling emergency obstetric situations requiring retrospective authorization
3. Denial Code: CO 11
Description: Diagnosis-Procedure Mismatch
This denial happens when the diagnosis code doesn’t clearly support the procedure or service provided. In obstetrics, this often occurs when the diagnosis code isn’t updated to match the current trimester, when complication codes are too vague to explain extra monitoring or services, or when the code doesn’t line up with the patient’s stage of pregnancy. For instance, using a first-trimester code for a third-trimester ultrasound can trigger an automatic denial based on insurer rules.
Prevention:
- Implement a protocol to update pregnancy diagnosis codes by trimester (Z34.0-, Z34.8-, O09.-)
- Create diagnosis-procedure mapping tools specific to common obstetric services
- Train providers and coders on proper use of high-risk and complication codes (O10-O16, O20-O29)
- Establish a review process for claims involving complications of pregnancy
- Use specific ICD-10 codes rather than general pregnancy codes when complications exist
4. Denial Code: CO 50
Description: Medical Necessity Denials
Medical necessity denials happen when an insurance company decides that a service wasn’t needed based on their guidelines. In obstetrics, this often applies to extra ultrasounds, non-stress tests, extended fetal monitoring, or hospital stays related to pregnancy. Insurance plans usually have set rules for what counts as medically necessary, and providers need to clearly document why the service was needed.
Prevention:
- Develop clear documentation templates that address medical necessity criteria for common high-risk services
- Train providers on proper documentation of risk factors justifying additional monitoring
- Create quick reference guides for medical necessity requirements by payer for common obstetric services
- Implement clinical protocols aligned with ACOG guidelines to support medical necessity determinations
- Document failed conservative management when advancing to more intensive monitoring
5. Denial Code: CO 16
Description: Claim Information Errors
These denials happen when claims are sent in with missing or incorrect details. In obstetrics, this often includes things like missing primary care provider info, wrong place of service codes, no birth weight listed for newborn care, incomplete global package data, or missing modifiers for obstetric services. Because maternity care often involves multiple providers and bundled billing, the chances of these errors and denials go up.
Prevention:
- Implement claim scrubbing software with obstetrics-specific edits
- Create comprehensive checklists for obstetric billing requirements
- Train staff on proper use of modifiers for obstetric global packages, partial services, and multiple gestation
- Verify patient demographics and insurance information at each trimester
- Create standardized documentation templates for antepartum, delivery, and postpartum care
6. Denial Code: CO 27
Description: Patient Eligibility Issues
Eligibility denials happen when services are provided to patients whose insurance coverage has ended or changed. These denials are more common in obstetrics because pregnancy care lasts several months, during which patients might change jobs, switch insurance plans, or lose coverage. Some patients may also qualify for special pregnancy-related coverage, like Medicaid, which has specific eligibility rules and coverage periods.
Prevention:
- Verify insurance eligibility at the initial visit and each trimester
- Implement real-time eligibility verification technology
- Create protocols for handling mid-pregnancy insurance changes
- Train front desk staff to inquire about potential coverage changes at each visit
- Develop patient education materials about reporting insurance changes promptly
7. Denial Code: CO 22
Description: Coordination of Benefits Problems
Coordination of benefits (COB) denials happen when it’s unclear which insurance is the primary one when a patient has more than one coverage plan. In obstetrics, these denials are more common due to insurance changes during pregnancy, dual coverage under both the patient’s and spouse’s plans, or secondary Medicaid coverage for pregnant women. Because pregnancy care spans several months, there’s a higher chance of insurance changes or added coverage during that time.
Prevention:
- Verify insurance at the first prenatal visit and each trimester
- Implement thorough insurance verification processes that identify all potential coverage sources
- Document primary versus secondary insurance status clearly
- Train front desk staff on COB rules specific to pregnancy coverage
- Create protocols for handling mid-pregnancy insurance changes
8. Denial Code: C0 29
Description: Timely Filing Violations
Late filing denials happen when claims are submitted after the payer’s deadline has passed. These deadlines can vary widely, from 30 days to a year after the service date. For obstetric practices, submitting claims on time can be especially tricky because the global maternity care package is usually billed after delivery, even though services are provided throughout the pregnancy. This longer time frame increases the chances of missing deadlines, particularly when complications or patient transfers occur.
Prevention:
- Create a comprehensive filing deadline calendar organized by payer
- Establish protocols for tracking antepartum care provided during the global period
- Implement electronic claims submission for faster processing
- Consider billing antepartum-only services for patients at high risk of transfer or insurance changes
- Train staff on global package billing timeframes by payer
9. Denial Code: C0 236
Description: Bundled Procedure Denials
These denials happen when procedure codes submitted together are seen as incompatible or incorrectly bundled according to coding rules. In obstetrics, this is common with cesarean deliveries that involve additional procedures, multiple surgeries during delivery, or billing for both delivery and postpartum services. Unlike global package bundling issues (CO-97), these denials are specifically about the correct relationship between procedures and the proper use of modifiers to show separate services.
Prevention:
- Stay current on NCCI (National Correct Coding Initiative) edits affecting obstetric services
- Train coders on proper use of modifiers (particularly -59, -51) for obstetric procedures
- Create procedure-specific coding guidelines for cesarean deliveries with additional procedures
- Implement claim scrubbing software that identifies potential bundling conflicts
- Develop clear documentation templates that support separate and distinct procedures
10. Denial Code: CO 204
Description: Non-covered Benefits
Non-covered service denials occur when a specific obstetric service is not included in the patient’s insurance benefits. Unlike medical necessity denials, these services are not covered, no matter the clinical need. In obstetrics, common non-covered services can include certain genetic tests, elective 3D/4D ultrasounds, experimental procedures, or services related to planned home births or birth centers, depending on the insurance plan. These denials are especially difficult because they often leave the patient responsible for payment.
Prevention:
- Verify specific coverage for planned services during the initial insurance verification
- Create a database of commonly non-covered obstetric services by payer
- Implement advance beneficiary notice (ABN) protocols for Medicare patients
- Develop similar financial responsibility forms for commercial payers
- Train scheduling staff to identify potentially non-covered services
Conclusion
For obstetric practices, managing these ten common denial reasons requires careful attention to the unique challenges of maternity care. The long duration of pregnancy, the complexities of global billing, and differences in insurance coverage all make billing and payment more difficult. To reduce denials, it’s important to verify insurance details early, keep accurate records throughout the pregnancy, improve communication between clinical and billing staff, and set up clear processes for handling high-risk pregnancies that involve extra services.
Running a denial analysis can help your practice figure out which issues are most affecting your revenue. With that insight, you can focus on fixing the areas that will have the biggest impact. Keep in mind that denial prevention isn’t something you do once—it needs ongoing tracking, regular staff training, and updates as insurance rules and care practices change. By making denial management part of your regular workflow, your practice can spend less time on paperwork and more time on patient care. This not only helps your bottom line but also supports better experiences for pregnant patients by reducing surprise bills and delays in care.