New Partnership Model Boosts Maternal Outcomes in Medicaid ACOs

Significant differences in maternal health outcomes were found in the Massachusetts Medicaid accountable care organization (ACO) program based on the ACO’s organizational structure, according to a recent investigation published in JAMA Network Open.¹

The study analyzed 2 distinct models implemented by the state in 2018: model A, a partnership between a health system and a managed care organization (MCO), and model B, which was primarily led by a primary care practice (PCP).

The researchers focused on the period between 2014 and 2020, analyzing Massachusetts All Payer Claims Database data for 67,204 Medicaid-covered deliveries (mean maternal age, 28.1 years). The objective was to estimate the differential association between these Medicaid ACO model designs—model A vs model B vs a non-ACO control group—and 6 key maternal health measures for quality of care, including severe maternal morbidity (SMM) and preterm birth.

Design Heterogeneity Showed Differential Results

The research team found that the structural differences between the 2 ACO models appeared to translate into measurable differences in outcomes. Model A, the health system-MCO partnership, was associated with a greater positive impact on some complex, system-level quality metrics compared with the non-ACO delivery group in the preimplementation period.

Specifically, the study demonstrated that model A was associated with a statistically significant reduction in SMM compared with the non-ACO group in the postimplementation period. SMM is a critical and composite measure encompassing unexpected outcomes of labor and delivery that result in significant short- or long-term consequences to a woman’s health, and the model A design showed a measurable advantage in this key clinical outcome.

Furthermore, model A was associated with decreased rates of prenatal emergency department visits (difference-in-differences [DID] IRR, 0.91; 95% CI, 0.84-0.98). This reduction suggested that the robust integration of resources—leveraging the administrative and network strength of an MCO along with the clinical capacity of a health system—effectively streamlined care coordination for high-risk pregnant and postpartum patients.

Conversely, model B, the PCP-led model, while still an important move toward value-based care, did not demonstrate the same level of statistical association with SMM reduction compared to the non-ACO group. The researchers noted that model B did not show a differential association for any of the delivery-related outcomes, including SMM and preterm birth. This finding suggests that while PCP leadership is vital, the capacity to influence systemwide change and coordination required for complex health measures like SMM may be constrained without the deeper infrastructure of a health system–MCO partnership. Changes in cesarean deliveries were inconclusive, with no other statistically significant changes in outcomes.

Focus on Preventive Care Showed Shared Success

While the models demonstrated differential performance on severe outcomes like SMM, the study indicated areas of shared success on measures related to preventive and coordinated care.

Both model A and model B were associated with higher utilization of primary care services in the postpartum period compared with the non-ACO control group. This is a critical finding, as the postpartum period is often characterized by fragmentation of care, and increased engagement with primary care can help manage chronic conditions and prevent future complications.

Specifically, both model A and model B were associated with an increased probability of postpartum depression screening (DID for model A, 6.11 percentage points [PP]; DID for Model B, 5.58 PP) compared with Medicaid non-ACO deliveries. Additionally, model A was associated with an increased probability of a timely postpartum visit (DID, 5.18 PP). Model B demonstrated its effectiveness in consistent utilization, associated with increased office visits during the prenatal and postpartum periods (eg, DID IRR for prenatal period, 1.10; 95% CI, 1.07-1.12). The researchers’ findings suggested that both ACO structures succeeded in improving outreach and access to necessary follow-up care for new mothers.

Policy Implications for Value-Based Care Design

“These findings suggest that Medicaid ACOs hold promise in improving some maternal health outcomes,” lead author Megan B. Cole, PhD, MPH, a member of the faculty at Harvard Medical School’s Department of Population Medicine, said in a news release.² “But their ability to do so may depend on how the ACO is designed.”

The study highlights the importance of thoughtful value-based care delivery design within Medicaid programs. With 37 states still without Medicaid ACOs and 13 considering changes, this research offers timely guidance for policy makers.

“As states and health systems consider how to improve maternal health care through value-based payment models, little evidence is available to guide them,” Cole added. “This study provides critical new evidence to state Medicaid programs, health systems, and policymakers as they consider how to design and implement Medicaid ACOs in a way that improves maternal health outcomes for low-income women.”

References

1. Cole MB, Lim K, Nguyen KH, et al. Medicaid accountable care model designs and maternal health measures. JAMA Netw Open. 2025;8(10):e2536565. doi:10.1001/jamanetworkopen.2025.36565

2. Medicaid innovation models improve care for moms, but design matters. News release. Harvard Pilgrim Health Care Institute. October 8, 2025. Accessed October 8, 2025. https://www.eurekalert.org/news-releases/1100918