CO-97 denials are common in OB/GYN billing. Here's what triggers them, how to appeal, and how to prevent recurrence.
A CO-97 denial means the payer considers a billed service to be bundled into the payment for another service already reimbursed. In OB/GYN billing, this shows up constantly around global maternity claims and postpartum visits billed separately when they shouldn't have been.
Common OB/GYN Triggers
The most frequent cause is billing a service separately that the payer considers part of the global maternity package — a postpartum visit, a routine antepartum check, or a procedure the payer bundles under a different code. For a deeper look at exactly what falls inside that bundle, see our [global maternity billing guidelines](/blog/understanding-global-maternity-billing-guidelines).
How to Fix an Existing CO-97 Denial
Start by confirming whether the service genuinely falls outside the bundle — sometimes it does, and the fix is an appeal with documentation showing the service was distinct (different date of service, unrelated diagnosis, or a documented complication). If the service is correctly bundled, the fix isn't an appeal — it's adjusting how the claim is submitted going forward.
Preventing Recurrence
CO-97 denials tend to cluster around the same handful of CPT codes once a practice has one. Running a focused review of your last 90 days of CO-97s, sorted by CPT code, usually reveals a pattern — often a single front-desk or coding habit repeated across many claims. Our detailed walkthrough on [fixing CO-97 denials in OB/GYN billing](/blog/co-97-denial-fix-obgyn) covers the appeal process step by step.
Key Takeaways
- ›CO-97 means the payer sees the service as bundled, not medically unnecessary
- ›Confirm bundling rules before appealing — sometimes the denial is correct
- ›Pattern-review denials by CPT code to catch recurring root causes
If CO-97 denials are a recurring line item on your aging report, it's worth having a dedicated [denial management](/denial-management) review of your last two quarters of EOBs to find the pattern before it costs another quarter of revenue.