Regionalization of maternity care by referring high-risk women to medical centers equipped to manage their unique comorbidities is one strategy proposed to curb the rising rate of maternal mortality.1–3 In 2015, the American College of Obstetricians and Gynecologists and the Society for Maternal-Fetal Medicine proposed classifying hospitals based on available clinical staff and resources as basic care (level I), specialty care (level II), subspecialty care (level III), and regional perinatal health care centers (level IV) to facilitate triage of patients at risk for maternal morbidity.4 (An update is available to reference 4. See Levels of maternal care. Obstetric Care Consensus No. 9. American College of Obstetricians and Gynecologists. Obstet Gynecol 2019;134:e41–55.) The Levels of Maternal Care concept draws on existing paradigms and evidence from the trauma and neonatology literature, but its potential utility in clinical obstetric practice is, by and large, unknown.5–7
Available evidence shows that pregnant women managed by experienced multidisciplinary teams of clinicians have better outcomes and links adverse perinatal events with delayed involvement of such specialists in the care of high-risk pregnant women.8–12 Although most states monitor premature birth by level of neonatal care, an analogous system is not in place to assess where women at risk for morbidity deliver.13 The logistics of patient transfer coupled with the potential loss of obstetric services in rural areas raise concerns about the implications of regionalization.14 Information on the current state of delivery care for women at high risk for maternal morbidity is warranted before making practice changes with perhaps unintended consequences. We therefore sought to estimate the degree to which women at high-risk for developing severe maternal morbidity are delivered at appropriate level of maternal care centers.
We conducted a cross-sectional study using linked data from the 2014 State Inpatient Database from the Healthcare Cost and Utilization Project and the 2014 American Hospital Association Annual Survey from Florida, Massachusetts, New Jersey, New York, North Carolina, Oregon, and Washington. The State Inpatient Database contains all inpatient admissions with associated demographics, diagnosis, and procedure codes for participating states.15 Select state databases within the State Inpatient Database contain a unique identifier to allow the linkage of inpatient admission to available data from the American Hospital Association. The American Hospital Association Annual Survey is completed by hospital administrators and contains information on the available inpatient, ambulatory, and ancillary services at a given hospital.16 The 2014 versions of the State Inpatient Database and American Hospital Association survey were selected owing to availability of the data sets with the consistent use of International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM) coding with available validation throughout the calendar year. Twenty-two states had State Inpatient Database data available from 2014 and contained an American Hospital Association identifier states for inclusion based on the ability of an American Hospital Association identifier in the State Inpatient Database allowing us to link the delivery hospital to the American Hospital Association survey data. We selected seven states for inclusion based on geographic location in the United States, geographic diversity of the rural and urban areas in each state, and variance in the maternal mortality ratio ranging from 5.0 for Massachusetts to 30.2 for New Jersey.17
We identified delivery hospitalizations using validated methodology described by Kuklina et al,18 and identified maternal comorbidities based on validated ICD-9 diagnosis codes. National guidelines were used to assign each woman to a minimum required level of maternal care (I to IV) based on her unique medical and obstetric comorbidities (Appendix 1, available online at http://links.lww.com/AOG/B466).4 Level I hospitals are those designed to care for uncomplicated pregnancies with the ability to detect, stabilize, and initiate management of unanticipated medical comorbidities (Box 1; note that Box 1 includes birth centers, which are not present in the State Inpatient Database and American Hospital Association data sets and therefore not included in our analysis). We therefore defined any chronic medical comorbidity complicating pregnancy as warranting a minimum of level II care. In addition to the obstetric conditions outlined in the guidelines, women with medical comorbidities such as hematologic disorders or drug abuse were assigned to a minimum level of maternal care II to reflect the possible need for the availability of medical consultants beyond the scope of general obstetric practice to guide management during the delivery hospitalization. A distinguishing characteristic between level of maternal care II and III hospitals is the ability to care for increasingly complex maternal medical comorbidities. We therefore assigned women with high-risk maternal medical conditions associated with high rates of severe maternal morbidity such as epilepsy, renal disease, autoimmune disease, or sickle cell disease as requiring a minimum level of maternal care of III to reflect the potential need for subspecialty care including the availability of cardiologists, neurologists, or the possibility of dialysis.19–23 Women with cardiac disease, cirrhosis, or high-risk neurologic disease were assigned a minimum level of maternal care of IV to reflect the possible need for surgical subspecialists including cardiac surgeons, neurosurgeons, or transplant surgeons in their care.24 Cardiac disease was defined using diagnostic codes associated with chronic conditions in an attempt to avoid inclusion of women with intrapartum cardiac events which would not have been anticipated antenatally.
We used a combination of ICD-9 procedure codes in conjunction with responses in the American Hospital Association survey to assign each delivering hospital to a unique level of maternal care based on available services (Appendix 2, available online at http://links.lww.com/AOG/B466). We required hospitals to have all services available to meet criteria for a given level. Level II or specialty care centers were characterized by the availability of general surgery services, a medical or surgical intensive care unit, and advanced imaging services, including ultrasonography, computed tomography, and magnetic resonance imaging. The availability of general surgery services was defined by the presence of procedure codes for common general surgical procedures such as appendectomy and cholecystectomy; the availability of imaging services was defined using both the presence of procedure codes in the State Inpatient Database and self-report of the presence of these services in the American Hospital Association survey. Level III or subspecialty care centers possessed all of the level II characteristics and benefitted from the presence of cardiology, neurology, and nephrology consultants as verification of the availability of subspecialty care as reported in the American Hospital Association. We distinguished level IV or regional perinatal centers from level III centers if transplant services, cardiac surgery, and neurosurgery were also available as reported in the American Hospital Association survey and verified by procedure codes from the State Inpatient Database. The American Hospital Association survey and State Inpatient Database are hospital-based data sets, precluding the inclusion of birth centers in the analysis.
Our primary outcome of interest was delivery at a hospital with an inappropriate level of maternal care based on obstetric risk and presence of comorbid conditions; for example, a patient with sickle cell disease delivering at a level II center instead of her assigned risk-appropriate level III care. Conversely, we categorized women delivering at a risk-appropriate level hospital or low-risk women delivering at a hospital with resources superseding her anticipated needs as receiving an appropriate level of maternal care.
Bivariate analyses were used to explore associations between hospital characteristics. SAS 9.4 statistical software was used for all analyses, and P<.05 was considered statistically significant. Because the data used in this analysis were de-identified, the research protocol was exempt from institutional review board approval by the Partners Human Research Committee.
The analysis included 845,545 deliveries occurring at 556 hospitals—23.2% level I, 46.6% level II, 21.9% level III, and 8.3% level IV by our level of maternal care classification (Table 1). Most women delivered at level II or III hospitals (33.8% and 36.0%) with a lower percentage of deliveries at level I and IV hospitals (12.3% and 17.9%), respectively. The majority of women (85.1%) had risk factors appropriate for delivery at level I hospitals with relatively few patients warranting delivery at level III or IV centers (1.9% and 0.4%, respectively).
Overall rates of comorbidities warranting delivery at level III hospitals such as placenta previa with prior uterine surgery or preterm preeclampsia with severe features were low overall (Table 2). Maternal morbidities warranting delivery at level IV centers such as maternal cardiac disease or brain tumor were exceedingly rare even before accounting for the potential to provide risk-appropriate care at level III hospitals for less severe variants of disease. Rates of medical and obstetric morbidity were lowest at level I centers and highest at level III centers; similar rates for the majority of morbidities were found in level II and level IV centers. The prevalence of maternal medical diseases such as cystic fibrosis, human immunodeficiency virus, and maternal malignancy tended to be highest at level IV centers.
Level I and II hospitals were smaller and a higher percentage were in rural than urban areas, whereas level III and IV centers were larger hospitals located in urban areas (Table 3). Hospitals' median annual delivery, transfer, and surgical volumes as well as the number of full-time intensivists increased with increasing level of maternal care. The majority (50.4%) of level I centers performed fewer than 500 deliveries annually, 1,000–4,000 annual deliveries was the most commonly encountered delivery volume at level II, level III, or level IV centers. Level I and II hospitals did not have neonatal intensive care units, whereas they were available at level III and IV centers. All level III and IV centers had both cardiac and medical or surgical intensive care units available.
Overall, the majority (97.6%) of women delivered at hospitals with an appropriate level of maternal care, with only 2.4% of women overall delivering at hospitals with an inappropriate level of maternal care; the latter ranged between 1.3% and 4.2% by state (Table 1). However, 43.4% of the 19,988 women with high-risk conditions requiring level III or IV care delivered at hospitals with an inappropriate level of maternal care. This percentage also varied by state, ranging between 33.0% and 63.6% (Appendix 3, available online at http://links.lww.com/AOG/B466).
Rates of delivery at inappropriate centers were lowest for women with hypertensive disorders of pregnancy at preterm gestations (Table 4). Rates of inappropriate delivery for women in this category ranged from 14.7% for women with preterm preeclampsia without severe features to 17.8% for those with preterm preeclampsia with severe features reflecting the need for a higher level of care with increasing complexity. Only 18.6% of women with placenta previa without prior uterine surgery were delivered at inappropriate centers compared with 37.7% of women with a placenta previa and prior uterine surgery. Rates of delivery at inappropriate centers were highest for women with chronic medical conditions such as maternal cardiac disease (68.2%).
Our results reveal that 97.6% of women have risk factors appropriate for care at level I or II hospitals with only 2.4% of deliveries occurring at hospitals with an inappropriate level of maternal care. However, a substantial fraction of women at high risk for severe maternal morbidity (as high as 68.2%) deliver at hospitals with inappropriately low level of maternal care. Despite the low percentage of overall deliveries, women with comorbidities particularly vulnerable to severe maternal morbidity or mortality, such as those with cardiac disease or placenta previa with prior uterine surgery, are at the highest risk of delivery at an inappropriate level center. The strong association between maternal medical or obstetric conditions known to benefit from multidisciplinary expertise and inappropriate level of maternal care stands out as priority for providing women with risk-appropriate obstetric care.8–10 These data provide reassurance about the potential effect of regionalization while suggesting the need to promote the appropriate triaging and referral for risk-appropriate care of high-risk obstetric patients in the United States.
This analysis builds on the guidelines set forth in the expert recommendations and provides a framework for the possible changes required to implement regionalization.4 One theoretical concern about regionalization is the operational and financial effect of shifting patients away from low-volume centers.14,16 Prior work associates low hospital delivery volume with higher rates of adverse outcomes, including severe maternal morbidity or failure to rescue.7,23–27 Concerns for higher rates of adverse outcomes at low-volume centers leave many to interpret regionalization as synonymous with transfer to high-volume centers. Our analysis documents the availability of many hospital services at level I centers. These findings coupled with the relatively low number of high-risk women warranting referral or transfer to higher levels of care should reassure those concerned about the financial and operational effect of shifting deliveries from low-volume centers.
The strength of the study is use of contemporary, large population-based data linked with information captured by American Hospital Association annual surveys from seven states that are diverse with respect to region, size, urbanity, and, as a result, racial, ethnic, and sociodemographic composition. There is no national-level data set available for linkage to the American Hospital Association or with the granularity of hospital-level data provided by the American Hospital Association survey. We therefore selected these states in an attempt to create a nationally representative sample. Limitations of our study stem mainly from the challenge of classifying hospitals' levels of care and patients' needs for risk-appropriate care. Pilot data from the Levels of Care Assessment Tool developed and implemented by the Centers for Disease Control and Prevention suggest that the level assigned by hospital self-assessment matched the onsite review only 50% of the time.28,29 The hospital level of maternal care designations for our study were derived from hospital self-reported characteristics in the American Hospital Association survey, which lacked information on the availability of some resources and personnel outlined in the consensus statement. To address this limitation, we attempted to validate hospital reports of available services with procedure billing codes available in the State Inpatient Database.
We recognize that there are elements proposed for use to designate hospitals' maternal levels of care, including availability of specific types of personnel (eg, maternal–fetal medicine, obstetric anesthesia, or obstetric nursing specialists) that we cannot capture using our data sources, which have led to hospitals' level of maternal care misclassification; conversely, with regard to available clinical services, the risk of such level of maternal care misclassification bias is lower. Maternal levels of risk were defined using ICD-9 Clinical Modification codes used for billing, which may be incorrect or vary in completeness, and do not capture the severity of specific conditions. Thus, for some conditions, such as cardiac disease or other maternal medical conditions, we may have misjudged the risks associated and the need for a different level of maternal care. If the study overestimates the need for referral or transfer to higher level centers, our findings would provide further reassurance about the effect of regionalization on our current health care system.
The goal of care regionalization is to improve maternal outcomes, not to simply deliver women at an “appropriate” level center. Our purposeful outcome selection (ie, inappropriately low level of delivery hospital) was for an initial analysis of available data and a step forward to improve our understanding of the national maternity care landscape and did not give consideration to maternal outcomes. If regionalized maternal care systems are already in place, one would expect women with more severe illness to deliver in level III and level IV hospitals. Without ability to adjust for disease severity and account for local referral patterns, a simple comparison may suggest to some that delivery at centers with an appropriate level of care actually worsens maternal outcomes. Studies examining maternal outcomes as a function of women receiving risk-appropriate maternity care with careful attention to disease severity and the potential for residual confounding as well as those considering the role of geography in local referral patterns are important directions for future research.30,31
The obstetric community's consensus in defining levels of maternal care in the United States was a critical first step towards improving maternal outcomes and one that acknowledged that questions of implementation feasibility and success are to be unanswered.4 Based on our study, the absolute number of women warranting referral and transfer to risk-appropriate care appears to be manageable, without overhauling our entire maternity system. Targeting women with high-risk medical conditions for transfer and risk-appropriate care is a logical and relatively simple step to improve maternal outcomes. These findings should offer reassurance for clinicians and policymakers about the potential feasibility and success of regionalization of maternity care in the United States.
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