What Are the CMS Proposed G-Codes for Obstetric Billing?
In the CY 2027 Medicare Physician Fee Schedule proposed rule published July 14, 2026, CMS included new HCPCS G-codes that would preserve the existing global obstetric package payment structure alongside the new CPT codes developed by the AMA and ACOG. If finalized, this would create two parallel billing systems for maternity care starting January 1, 2027: the new granular CPT framework that bills antepartum, labor management, delivery, and postpartum separately, and a set of G-codes that maintain the old bundled global approach. ACOG has warned that this dual system would increase administrative confusion, worsen obstetric care disparities, and undermine the restructure that took nearly two years to develop.
Why ACOG opposes the G-codes: ACOG argues the G-codes would allow payers to default to the lower-paying global package rather than adopting the new CPT codes, defeating the purpose of the restructure. Practices would need to maintain two billing workflows indefinitely.
Where it stands now: The public comment period on the CY 2027 proposed rule closed September 14, 2026. CMS is reviewing the comments received and could narrow, revise, or withdraw the G-code provision in the final rule expected November 2026.
What practices should do now: Continue preparing for the new CPT codes effective January 1, 2027. Contact your payers to ask whether they plan to adopt the new CPT codes or default to G-codes. Track the final rule expected in November 2026.
How the Dual System Proposal Emerged
The backstory makes the conflict clear. In April 2026, the AMA CPT Editorial Panel approved a comprehensive restructure of maternity care coding, developed in collaboration with ACOG and multiple specialty societies over nearly two years. The new framework replaces the legacy global obstetric package (CPT 59400, 59510, 59610 and their variants) with individual codes organized around four distinct phases: antepartum care, labor management, delivery, and postpartum care. The intent was to capture the actual complexity and variability of modern obstetric practice, including team-based care, telehealth visits, remote monitoring, and individualized prenatal plans.
Then CMS published its CY 2027 proposed rule on July 14, 2026. Alongside the new CPT codes, the rule included proposed HCPCS G-codes that would effectively recreate the global package under a different code set. Practices billing Medicare would have the option to use either system. ACOG’s concern is practical: if Medicare offers a global-payment alternative, commercial payers will follow, and the incentive to adopt the more granular CPT framework disappears. The restructure becomes optional rather than universal, and practices that invested in the transition are competing against practices that stayed with the bundled approach. For background on the code changes themselves, see our 2027 OB/GYN billing code changes overview.
Why a Dual Billing System Creates Problems for OB/GYN Practices
Running two parallel billing systems for the same service is not a minor administrative inconvenience. It changes how every maternity claim is submitted, adjudicated, and reconciled. Here is what the dual system would mean in practice.
Two workflows for the same patient: A practice treating patients with both Medicare and commercial insurance would need to determine which billing framework each payer accepts before submitting every maternity claim. If Medicare uses G-codes and a commercial payer adopts the new CPT codes, the same delivery generates two entirely different claim structures.
Payer adoption fragmentation: Without a single standard, payers will adopt different code sets at different times. Some will move to the new CPT codes immediately. Others will default to G-codes because their adjudication systems are already built around the global package. The result is a patchwork where the billing team must track which system each payer uses, per patient, per claim.
Revenue risk from the global default: The global package pays a single bundled amount regardless of complexity. The new CPT framework pays separately for each phase, which means practices that handle high-risk pregnancies, extended antepartum monitoring, or complicated deliveries would earn more under the granular codes. If payers default to G-codes, that additional revenue disappears.
Training and documentation burden: Staff trained on the new CPT codes must also maintain proficiency in the old global package rules. Documentation requirements differ between the two systems. The risk of coding errors increases every time a biller must switch between frameworks.
Across the billing companies in our network, the most common question practice managers are asking right now is whether they should prepare for the new CPT codes, the G-codes, or both. The answer, until the final rule is published, is both. But the advocacy position from ACOG is clear: the G-codes should not be finalized, and practices should be preparing for the new CPT framework as the primary path forward. For practices already managing the modifier TH transition for antepartum billing, this adds another layer of uncertainty to an already complex changeover.
The 2027 obstetric billing transition is the most complex coding change OB/GYN practices have faced in decades. Whether CMS finalizes the G-codes or not, your billing team needs to be ready for the new CPT framework. Get matched with medical billing companies that specialize in obstetric coding, at no cost to your practice. Rates start as low as 2.95%.
What Your Practice Should Do Now
The comment period on the CY 2027 proposed rule closed September 14, 2026. CMS is now reviewing the comments received and will publish the final rule, expected in November 2026, which will determine whether the G-codes survive, are revised, or are withdrawn. While that decision is pending, here is what every OB/GYN practice billing maternity services should do now.
1. Contact your payers to ask whether they plan to adopt the new CPT codes or the G-codes (or both) starting January 1, 2027. Document their responses. If a payer has not decided, your inquiry signals demand for the new framework and gives you planning data.
2. Continue preparing for the new CPT codes. Train your billing staff on the four-phase structure (antepartum, labor management, delivery, postpartum). Update documentation templates to capture the data each new code requires. Do not pause your CPT transition to wait for the final rule.
3. If your practice has not yet started using modifier TH on antepartum E/M claims, begin immediately. The September 1, 2026 transition date recommended by ACOG has already passed.
4. Audit your current global OB package claims from the last 12 months to model how revenue would change under the new CPT framework versus the G-codes. This gives you concrete numbers for internal planning and payer negotiations.
5. Track the final rule. CMS typically publishes the Physician Fee Schedule final rule in early to mid November. The G-code provision could be finalized as proposed, revised based on comments received, or withdrawn entirely. Your billing workflow for January 1, 2027 depends on the outcome.
For a deeper understanding of the antepartum coding rules that apply during this transition period, see our guides on antepartum care billing with CPT 59426 and the OB/GYN Red Book.
What Is ACOG’s Position on the G-Codes?
ACOG has publicly opposed the CMS G-code proposal, arguing that it undermines a restructure that was developed through extensive collaboration between the AMA, ACOG, and multiple specialty societies. The organization’s primary concerns are:
1. The G-codes create a path for payers to avoid adopting the new CPT codes, which were designed to more accurately capture the clinical complexity and variability of modern obstetric care.
2. A dual system perpetuates the limitations of the global package, which pays the same amount regardless of whether a pregnancy is routine or high-risk, and regardless of the number of antepartum visits or the complexity of the delivery.
3. The administrative burden of maintaining two parallel billing systems falls disproportionately on smaller practices that lack dedicated coding staff.
4. The G-codes could worsen obstetric care disparities by allowing lower-paying bundled reimbursement to persist in regions and payer networks that serve underserved populations.
ACOG held a coding course on September 3, 2026 in Las Vegas specifically to help practices navigate the transition to the new obstetric codes. The fact that ACOG is investing in provider education on the new CPT framework while simultaneously opposing the G-code alternative signals that the organization expects the new codes to prevail in the final rule, but is preparing for the possibility that practices will need to manage both systems.
Frequently Asked Questions
Are the CMS G-codes already in effect?
No. The G-codes are part of the CY 2027 proposed rule published July 14, 2026. They are not finalized. The comment period closed September 14, 2026, and CMS is reviewing the comments received. The final rule is expected in November 2026. If finalized, the G-codes would take effect January 1, 2027.
Would the G-codes replace the new CPT maternity codes?
No. Both systems would exist simultaneously. Practices would have the option to bill using the new CPT codes or the G-codes for Medicare maternity claims. This is the core of ACOG’s concern: the dual system removes the incentive for universal adoption of the new framework.
Should my practice prepare for the G-codes or the new CPT codes?
Prepare for the new CPT codes first. The new framework is the AMA and ACOG standard and will be adopted by most commercial payers regardless of what CMS does with the G-codes. Track the final rule for G-code status, but do not delay your CPT transition to wait for the answer.
Will commercial payers follow CMS on the G-codes?
It depends on the payer. If CMS finalizes the G-codes, some commercial payers may adopt them as the easier path. Others will move to the new CPT codes because the granular structure gives them more data on maternity care utilization. Contact your top payers now to ask their plans.
Has the comment period on the proposed rule closed?
Yes. The comment period for the CY 2027 Medicare Physician Fee Schedule proposed rule (CMS-1848-P) closed September 14, 2026. CMS is now reviewing all comments received. The final rule is expected in November 2026 and will determine whether the G-code provision is finalized, revised, or withdrawn.
Does this affect the modifier TH transition?
The modifier TH transition (using modifier TH on antepartum E/M codes starting September 1, 2026) proceeds regardless of the G-code outcome. Modifier TH applies to E/M codes billed during the transition period and is not affected by whether CMS finalizes the G-codes.
Next Steps
Track the CMS final rule expected in November 2026 for the G-code decision. Contact your top payers to ask whether they will adopt the new CPT codes or the G-codes. Continue training your billing team on the new four-phase obstetric coding framework.
For the full picture of the 2027 code changes, see our OB/GYN billing code changes overview. For the modifier TH transition timeline, see our modifier TH antepartum billing guide.
The 2027 obstetric billing landscape is still being written. Whether CMS keeps the G-codes or drops them, your practice needs a billing partner that can handle whatever system your payers adopt. Get matched with OB/GYN billing companies that are already preparing for the transition, at no cost to your practice. OB/GYN Bill Co is powered by Billing Service Quotes, with rates starting as low as 2.95%.
