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Both low-risk and high-risk obstetric patients at low-volume hospitals in rural counties had higher risk for severe maternal morbidity (SMM) compared with rural hospitals delivering more babies, a retrospective cross-sectional study revealed.

For patients in low-volume rural hospitals, the adjusted risk ratio [ARR] for severe pregnancy complication was 1.65 (95% CI 1.14-2.39) compared with high-volume rural hospitals.

For medium-volume hospitals, the ARR for SMM was 1.37 (95% CI 1.10-1.70), and for medium-high volumes, it was 1.26 (95% CI 1.05-1.51), reported Katy Backes Kozhimannil, PhD, MPA, of University of Minnesota School of Public Health, Minneapolis, and co-authors.

The research, which was published in , used data from more than 11 million urban births and more than half a million rural births in California, Michigan, Pennsylvania, and South Carolina.

"These findings imply a need for tailored quality improvement strategies for lower-volume hospitals in rural communities," the researchers concluded.

Co-author Stephanie Leonard, PhD, an epidemiologist of Stanford University's Dunlevie Maternal-Fetal Medicine Center, noted this research adds to the growing body of work trying to understand why the U.S. has worse SMM rates than other high-resource countries and helps identify "levers that can be pulled" to improve outcomes.

"We're saying that, yeah, having a lower volume plus being in a rural area -- this is a group of hospitals that needs support and needs attention because people in those areas need quality obstetric services too," Leonard said in an interview with 麻豆传媒.

Shon Rowan, MD, of West Virginia University in Morgantown, agreed that targeted improvement strategies would be beneficial. Rowan, who was not involved with the study, noted that the (AIM) is one organization doing such work.

"This study was done on larger states, which shows that this is a nationwide issue. And it shows the importance of programs like AIM and being engaged in sharing resources and information with other states so that we all have that common goal of decreasing morbidity," Rowan told 麻豆传媒."I think it lets us know that we need to maybe divert even more resources to these small hospitals."

To Rowan, the present findings also affirm that West Virginia isn't alone in these alarming trends.

He said that in rural states like West Virginia, there are many obstetric care deserts where people have to travel too far to receive care. "It's not unheard of for a patient to drive 2 to 3 hours to a delivering facility. And that's leading to more patients showing up in emergency rooms that don't have the resources," he said.

For their study, Leonard and colleagues created a database that combined vital records and hospitalization data from four large states: California (from 2004 to 2018), Michigan (from 2004 to 2020), Pennsylvania (from 2004 to 2014), and South Carolina (from 2004 to 2020).

In urban counties, hospitals that delivered 10-500 births were defined as low volume, 501-1,000 as medium, 1,001-2,000 as medium-high, and more than 2,000 as high volume. In rural counties, 10-110 annual births were considered low volume, 111-240 were medium, 241-460 were medium-high, and more than 460 were considered high volume.

SMM was defined according to CDC parameters and generally included unexpected outcomes of labor and delivery that result in significant short-term or long-term health consequences, excluding blood transfusion.

In urban hospitals, SMM rates ranged from 0.73% in high-volume (over 2,000 births per year) to 0.50% in low-volume hospitals (10-500 births). In rural hospitals, that range spanned from 0.47% in high-volume to 0.70% in low-volume hospitals.

For either low-risk or higher-risk patients who gave birth at urban hospitals, there was no statistically significant association between birth volume category and SMM.

Leonard stressed to 麻豆传媒 that obstetric patients at low risk -- defined as having none of 27 comorbidities such as advanced maternal age or placenta accreta spectrum -- were actually at particularly high risk in rural hospitals with relatively few deliveries. "If they gave birth at a low-volume rural hospital, they were at over twice the risk of having severe maternal morbidity, as a similar person who delivered at a high-volume rural hospital," she said.

Stratified by the delivery volume in rural hospitals, the ARR for SMM in low-risk obstetric patients was 2.32 (95% CI 1.32-4.07) in low-volume hospitals, 1.66 (95% CI 1.20-2.28) in medium-volume hospitals, and 1.68 (95% CI 1.29-2.18) in medium-high volume hospitals, all compared with high-volume rural hospitals.

Authors acknowledged that defining rurality is tricky and that rural and urban don't necessarily exist as a dichotomy, although that is how they stratified the data.

They also note that although the four states analyzed are a quarter of all births in the U.S., highly rural states could have different results. Data reporting was also not completely consistent across states and did not contain comprehensive information about patient referrals or transfers, which limits the researchers' understanding of those factors' influence.

Leonard noted that future research should look at differences in prenatal and postpartum care, as well as further analyze the role of people's identities.

"It's already been well shown that in rural communities that have substantial populations of Black and Indigenous people, you see the highest rates of severe maternal morbidity," Leonard said. Therefore, she continued, more research documenting the intersections of race, ethnicity, and rural versus urban status "certainly is a big area that needs attention."

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