See Editorial, p 844
At midcareer, it dawned on me that I could no longer continue work as a maternal–fetal medicine specialist. Assuredly, there was an element of “burnout,” after decades managing complex pregnancies, high-risk deliveries, a busy outpatient practice, and a demanding university faculty appointment. More so was the realization that I was simply in the wrong specialty. My title then was “Director of Prenatal Diagnosis,” and my academic work was mainly in fetal medicine. What had originally attracted me to maternal–fetal medicine, however, was the unique, and arguably underserved, discipline of what I will call “Maternal Medicine,” the focused care of women experiencing medically complicated pregnancies. That realization was nearly 15 years ago. Since then, I have retrained in anesthesiology, focusing my efforts in obstetric anesthesia and, in that way, have managed to continue the practice of maternal medicine. This unusual career trajectory, from obstetrician to clinical geneticist and maternal–fetal medicine specialist, and finally to obstetric anesthesiologist, provided a thought-provoking perspective on the profoundly changing face of obstetric medicine in the United States during the past 30 years, and on the attendant crisis in maternal medicine.
FROM OBSTETRICIAN TO ANESTHESIOLOGIST
My training in obstetrics, with subsequent fellowships in maternal–fetal medicine and clinical genetics, began in the 1980s, a time when rapid advances, particularly in ultrasound, were radically transforming obstetrical practice and philosophy.1 Before that time, assessment of the fetus was mainly inferred by hands-on physical examination of the mother, occasionally using a small number of now-antiquated maternal serum and urine biochemical tests (maternal serum estriols, and placental lactogen) that weakly predicted quality of placental function, and using rudimentary electronic monitoring of the fetal heart rate and its variability over time. Combining these indirect fetal evaluations with published data about pregnancy outcomes among patient-sets grouped by maternal maladies such as diabetes mellitus, hypertension, or renal disease provided the limited basis for prognosticating about the fetus and, from there, divining the timing of relatively uncommon interventions on its behalf. Otherwise, an obstetrician’s full attention was on the maternal patient, reasoning that, if she were well, likely so too was her unborn baby.
With the subsequent introduction of high-resolution ultrasound imaging, the fetus could be examined in real time and in detail. This allowed accurate assessment of gestational age, plurality, anatomy, blood flow, and growth. Fetal interventions, such as periumbilical blood sampling and transfusion, became increasingly safe and commonplace.1,2 Accordingly, philosophically and psychologically, there occurred a fundamental shift in obstetrical medicine’s collective conceptualization of the “maternal–fetal dyad.”3 Previously, the fetus was thought of as an important, but mainly inferred, passenger whose welfare was dependent on, but of secondary concern to, that of the mother. Now its status was elevated to that of an individual second patient deserving its own medical examination, and sometimes its own interventions, even if those interventions entailed significant maternal risk.4
For a while, many of us in the specialty tried to hold on to a balanced maternal and fetal maternal–fetal medicine model of practice, continuing to attend to in-hospital high-acuity maternity care, despite the rapidly expanding time demands in a mostly office-based world of fetal medicine. This paradigm necessitated frequent disruptions, due to divided attention between inpatient and outpatient demands by day, often followed by all-night hospital-care delivering or managing sick maternity patients, only to return the following day to an office full of patients. Research and administrative duties were fit into one’s nonclinical “free time.” It was an exhausting way of life, and for a growing number of maternal–fetal medicine specialists, including me, became unsustainable. Many maternal–fetal medicine groups began limiting their hospital availability.5 It became commonplace to give up primary responsibility for intrapartum care and, in some instances, all but consultative in-hospital maternal care while focusing more and more on fetal medicine.
I chose a different route. Around the time of my disenchantment, I befriended an intensivist who was a professor of anesthesiology at my institution. He and I had toiled several days managing to rescue, while avoiding liver transplantation, a critically ill postpartum patient suffering multiorgan failure secondary to acute fatty liver of pregnancy. During this encounter, sharing our different, but complementary, perspectives and interventions, I came to fully appreciate an anesthesiologist’s life-saving skill set and how profoundly those skills could impact the outcome of medically complex obstetrical cases. And with that discovery, at 47 years of age, I chose to begin anew and retrained in anesthesiology to maintain my lifelong focus on maternal medicine.
THE MATERNITY CARE CRISIS IN THE UNITED STATES
It was during my subsequent anesthesiology residency, commencing in 2003, that credible reports of rising maternal mortality and morbidity in the United States first came to my attention.6 Because of recognized problems in case ascertainment and comparatively poor quality of American maternal mortality data, many clinicians were initially skeptical. By 2010, a maternity-care crisis in the United States became undeniable,7 and the problem has continued to worsen.8 Indeed, recent data indicate that the United States has, by far, the highest maternal mortality ratio of any resource-rich nation.8,9 Its rate of major obstetric morbidity, likewise, is remarkably high and continues to rise.9,10 Moreover, the United States experience contrasts with most of the rest of the world, where maternal outcomes continue to improve, even though US health care expenditures exceed those of any other nation.11
To be fair, it is widely accepted that, over recent decades, the average American gravida has become older, as well as more often obese or severely obese.12,13 Consequently, associated chronic conditions (hypertension, diabetes mellitus, obstructive sleep apnea, asthma, intrinsic cardiac, and renal disorders) have also become more frequent and commonly more serious. Meanwhile, medical and surgical advances have allowed more women to survive well into reproductive age affected by complex inherited and/or chronic pediatric conditions (ie, congenital heart disease, cystic fibrosis, sickle cell disease, juvenile diabetes, organ transplant recipients), and such women often choose, despite risk, to endure pregnancy. Still, it must be acknowledged that these factors alone cannot fully account for the variance between the United States and better-performing countries. Indeed, other wealthy nations face similar demographic changes without rising maternal morbidity and mortality. More unique to the United States, among rich nations, is an increasing prevalence of harmful public health realities including poverty, poorly understood racial disparities documented to adversely impact obstetrical outcomes independent of social class, epidemic opioid abuse, and mounting barriers to access of high-quality contraception, preconception, prenatal, and extended postpartum care.14
Nevertheless, recent reports and commentaries have suggested that there remain opportunities for in-hospital interventions that could lead to markedly improved maternal outcomes, even while awaiting more equitable access.15,16 In-hospital maternal death and major morbidity often represent instances of potentially remediable failures to rescue, defined as (1) death after in-hospital adverse occurrence,17 or (2) any situation where the clinical team was unable to mitigate preventable harm to patients.18 Consequently, efforts to optimize maternal in-hospital care, and particularly capacity to rescue, could reverse our unacceptable trends in adverse maternal outcomes.
LESSONS FROM THE CALIFORNIA MATERNAL QUALITY CARE COLLABORATIVE: ADDRESSING FAILURE TO RESCUE, AS AN OPPORTUNITY FOR IMPROVEMENT
Creating strategies to address pregnancy-related adverse outcomes require detailed understanding of where, when, and how these events unfold. Beginning in 2004, the California Maternal Quality Care Collaborative, using an enhanced pregnancy-related death surveillance methodology and a multidisciplinary committee review of individual patient medical records, accomplished perhaps the most focused study of pregnancy-related maternal mortality in a large region of the United States to date. They found that deaths occurred outside of a health care setting only 5% of the time,19 and judged that 41% of cases had a “good to strong” chance, while 90% had at least “some chance” of preventability.20 Leading causes included cardiovascular conditions (including peripartum cardiomyopathy), obstetrical hemorrhage, preeclampsia, venous thromboembolism, amniotic fluid embolism, and maternal sepsis. Estimates of preventability varied according to cause, ranging from a low likelihood for amniotic fluid embolism to a high likelihood for obstetrical hemorrhage, preeclampsia, sepsis, and venous thromboembolism. Importantly, when looking at specific care-related elements contributing to mortal outcomes, health care provider factors, including “delayed response to clinical warning signs,” “misdiagnoses,” and “ineffective treatment decisions,” dominated for all 6 etiologies.20 Here it is striking that many deaths were indeed failures to rescue insomuch as they were deemed “preventable,” and they typically occurred in settings where lifesaving resources should have been promptly afforded.
Commendably, in response to their findings on causes of maternal mortality, the California Maternal Quality Care Collaborative established a statewide program to improve maternal care in California.20 This effort included creation and deployment of safety bundles guiding standardized and evidence-based management of the commonest, yet most preventable, causes of maternal death and injury. The California Maternal Quality Care Collaborative now supports programs for both patient and provider education emphasizing essential knowledge, communication, and teamwork. Since 2008, simultaneous with California Maternal Quality Care Collaborative outreach efforts, California has seen a remarkable decrease in maternal mortality, despite continued increasing rates observed elsewhere in the United States.20,21 Examining the mechanism of the California Maternal Quality Care Collaborative’s success, Main et al22 found that the personnel resources committed to bundle deployment were just as important as the specific changes within each safety bundle. These include training of interdisciplinary teams, simulation drills, and hospital mentorship by physician/nurse pairs with expertise in maternal quality improvement. The California Maternal Quality Care Collaborative experience showed that we can engineer safety bundles for the commonest events, which if satisfactorily deployed, are likely to improve outcomes; however, human factors remain an essential element to effective maternal rescue.
IDENTIFYING A “RIGHT-SKILLED” WORKFORCE TO OPTIMIZE MATERNAL OUTCOMES
While it is obvious that obstetrical care facilities need clinicians skilled in the surgical and basic medical aspects of obstetrics, and safety systems to standardize care delivery, the California Maternal Quality Care Collaborative mortality data implicating “delayed response,” “misdiagnoses,” and “ineffective treatment decisions” (presumably by such clinicians) also suggest that these skills alone are not sufficient.
To avert preventable mortalities and morbidities, it appears that teams must also be rapidly available on-site and capable of expertly addressing the complex medical and resuscitative aspects of life-threatening peripartum events. Moreover, to function optimally, these teams need leaders whose medically sophisticated, yet obstetrically oriented diagnostic and critical care skills ensure (1) early recognition of evolving maternal crises, (2) appropriate escalation of monitoring, when necessary, and (3) orchestration of team-supported life-saving and morbidity-limiting treatments. Such team leaders would be capable of initiating and directing effective maternal rescue. But, in this era, who are these maternal medicine proficients and crisis-capable leaders? Are there enough of them to address a nationwide crisis? And how might such leaders help generalize the California experience to the rest of the United States?
EMBRACING AN INTERDISCIPLINARY LEADERSHIP APPROACH TO HOSPITAL MATERNAL MEDICINE
In the early decades of my career, general obstetricians concentrated mainly on the surgical and straightforward medical aspects of obstetrical care, while medically complex and critical care of mothers was largely the purview of maternal–fetal medicine specialists. But over time, with heightened focus on the fetal patient, interest and capacity among maternal–fetal medicine specialists to provide maternity-specific care has waned,5 particularly in-hospital maternal medical management. Inopportunely, this shift in focus happened to coincide with the national trend toward increasing medical complexity of obstetrical patients.
Leaders in maternal–fetal medicine have called on the profession to reinvigorate maternal medicine. In 2013, D’Alton et al23 called for “Putting the ‘M’ back into maternal–fetal medicine.” The authors conceded that maternal–fetal medicine has already witnessed a remarkable shift toward “increasing popularity of outpatient, consultative practice,” possibly motivated by “predictable hours,” “vast reimbursement differential,” and a “marked disparity in medicolegal burden,” that one enjoys in outpatient/consultative practice compared with more onerous inpatient care of complex maternity patients. Although there do remain maternal–fetal medicine physicians whose principle focus is maternal medicine, including in-hospital complex medical and obstetrical care, survey data indicate that these individuals are increasingly rare.24
One alternative to continuous in-hospital availability of maternal–fetal medicine specialists has been to substitute clinicians from the relatively new specialty of “obstetrical hospitalists” for the inpatient aspect of complex and emergency maternity care.25 This obstetrical-hospitalist model has accrued limited evidence crediting it with improvement in overall obstetrical outcomes.26 However, it is unlikely that it can address the care gap for women having the highest levels of medical complexity, and particularly those needing rapid deployment of resuscitation or critical care. While obstetrical-hospitalists clearly have ample training and experience in general obstetrics, they typically do not have advanced training or experience in either the complex medical complications coincidental with pregnancy or in maternal critical care. In fact, many of their generalist obstetrician colleagues perceive this deficiency: A survey of American College of Obstetrics and Gynecology fellows found >60% were not “comfortable” having their obstetrical-hospitalists providing care to women with complex medical conditions.27
ANESTHESIOLOGISTS’ ROLE IN THE INTERDISCIPLINARY MATERNITY CARE TEAM
From my perspective as a former obstetrician and current practicing obstetric anesthesiologist, with more than 30 years’ experience observing and participating in labor and delivery processes, it is evident that, among clinicians in the maternal care team (maternal–fetal medicine, obstetrical-hospitalist, general obstetrician, midwife, or nurse), the physician anesthesiologist is ideally suited, and absolutely critical, for the efficient and reliable management of medical aspects of rescue care for the maternal patient. Anesthesiology training and the nature of its practice emphasize advanced lifesaving and life-supporting critical care skills. Examples of such skills, that are critical in obstetric emergencies, include (1) rapidly establishing difficult emergency IV access, (2) safely inserting, and interpreting physiologic data from, arterial and central venous catheters, (3) performing expert pharmaceutical titration during critical hemodynamic derangement, (4) facilitating complex blood product replacement, and (5) leading all aspects of airway management, and cardiopulmonary resuscitation. Moreover, anesthesiologists have long championed hospital safety with an eye to continuous quality improvement, team skills, a culture embracing interdisciplinarity, and a systems orientation that prepare them for crisis team leadership or participation.
THE ESSENTIAL CHALLENGE OF MATERNAL MEDICINE
Nevertheless, this is an area of anesthesiology that has extremely high stakes (2 lives) and often involves morally complex decisions. The medical and ethical implications of pregnancy, including both normal and pathological adaptations to pregnancy and the “2 in 1” patient implications of the maternal–fetal dyad, require modification of the anesthesiologists’ skill set to optimally manage the complications and crises that befall maternity patients. At first blush, one might think that maternal medicine and maternal resuscitation should not be complicated. After all, many of the medical issues faced by pregnant women are the same conditions faced by nonpregnant reproductive-aged women. Pulmonary embolism complicating pregnancy, for example, is still pulmonary embolism. But, to the contrary, it takes experience and a practiced cognitive discipline to become adept at simultaneously considering the maternal patient and the fetal patient, while deciding best management when all manner of coincidental or pregnancy-specific medical complications arise. This is the essential challenge of maternal medicine. Interventions taken on behalf of the maternal patient necessarily affect the fetal patient residing within her, while interventions on behalf of the fetus often endanger the mother. The interdependence within this dyad is absolute, while risk-to-benefit considerations for the mother on the one hand, and for her fetus on the other, are commonly, and perplexingly, in opposing directions.3,4 This dilemma, balancing risks within the maternal–fetal dyad, sometimes delays critical decision-making and therapeutic interventions. At other times, the dilemma can drive conflict between and among members of the clinical team; even worse, it may engender distrust between the obstetric patient and her team of providers.
Maternal medicine–focused clinicians, regardless of specialty training (maternal–fetal medicine, internist, obstetrician, or anesthesiologist) possess essential medical expertise, but also tacit knowledge, cultivated by experience, to anticipate and productively navigate these complex decisions as members of cohesive team, in partnership with the women and families they serve. All anesthesiologists possess essential skills in anesthesia and resuscitation for obstetric patients. However, it is the established and growing subspecialty of obstetrical anesthesiology in which mastery of the scientific and tacit elements of maternal medicine converges in a primary career-long focus (Table).
OPTIMIZING COMPLEX OBSTETRICAL CARE: THOUGHTS ON REGIONALIZATION AND EXPANDING THE OBSTETRICAL ANESTHESIA WORKFORCE
Currently, immediate availability of obstetric anesthesiologists in US labor and delivery units is likely not the norm.28 While the recent Obstetric Anesthesia Workforce Survey concluded that >85% of hospitals with at least 1500 deliveries per year claim “in-house” continuous labor and delivery coverage by anesthesiologists, some experts believe that this reported “coverage” overestimates actual “immediate availability” (David Birnbach, University of Miami, personal communication, July 2017 and Jill Mhyre, University of Arkansas, personal communication, September 2017). In many instances, such labor and delivery coverage is oriented toward providing neuraxial labor analgesia, with that duty stacked on full hospital coverage responsibilities, including staffing nonobstetrical emergency cases, particularly at night and on weekends and holidays. This may not be surprising, in an era of decreasing hospital support for all manner of anesthesia services. Yet, given the unpredictable, time-critical, and not infrequent nature of maternal medical crises, the model of providing obstetrical anesthesia “coverage” while occupied by other off-unit clinical responsibilities, or by practitioners uninterested in and lacking knowledge about medically complex obstetrics, often leaves the maternal care team incomplete and likely needs to be rectified to assure best interdisciplinary maternal crisis care.
While it is impossible to eliminate all obstetric-related mortality and major morbidity, the findings of the California Maternal Quality Care Collaborative and others clarify that its burden can be substantially reduced by striving for nationwide optimization of hospital maternity care. For the most complex cases, such optimization requires multiple elements, including state-of-the-art facilities, sophisticated blood banking, and high-functioning interdisciplinary care teams. For low-risk women and low-volume delivery centers, such an approach is likely to increase costs with uncertain benefit; it is not realistic to expect that every hospital could devote the financial and professional resources to deliver such best achievable maternal care.28 Instead, regionalization of maternity care is presented as a solution to optimize resource allocation in the United States, as described in the Society of Maternal Fetal Medicine/American College of Obstetrics and Gynecology Obstetric Care Consensus report “Levels of Maternal Care.”29 In such a system, fully resourced regional centers are structured to not only optimally manage the most complex maternal cases but also to lead networks of referring facilities to implement safety bundles and other systems solutions to optimize maternal safety at all levels of care. Critical to the success of regional referral centers will be on-site, medically sophisticated clinicians fluent in maternal medicine and capable of rapidly orchestrating interdisciplinary escalation of care. Hospital systems, and anesthesiology as a specialty, should not underestimate the impact that obstetric anesthesiologists can have in making such a model come to fruition. The modern maternal-focused maternal–fetal medicine or subspecialty obstetric-hospitalist, in collaboration with a maternal medicine–focused anesthesiologist can, together, provide optimal team-leadership at both the hospital and regional level. Acknowledging and formalizing the coleadership role of obstetric anesthesiologists will complement and could rapidly advance the maternal safety efforts of the California Maternal Quality Care Collaborative, National Partnership for Maternal Safety,30 Society of Maternal Fetal Medicine, Society of Obstetric Anesthesiology and Perinatology, and others, nationally.
Undeniably, the rise of maternal morbidity and mortality in the United States extends beyond the puerperium, and encompasses the entire pregnancy and postpartum year. Some consequential aspects of antepartum and postpartum maternal care need to be addressed by obstetrical caregivers, and by society, throughout pregnancy and into an extended puerperium, including efforts to ameliorate the maternal/fetal consequences of economic deprivation and racial disparities.31 However, it is in the hospital where maternal medicine-focused and rescue-ready obstetrical anesthesiologists, in cooperation with fetal specialists and general obstetricians, can have the greatest impact on our contemporary crisis in maternal mortality and severe obstetric morbidity. Even while outcome studies supporting this paradigm remain to be undertaken, it cannot be disputed that preventing the main causes of pregnancy-related maternal death requires careful contingency planning, risk mitigation, and aggressive medical “rescue,” all areas where anesthesiologists excel. Hospitals and health care systems must recognize and support the added value of dedicated, on-unit, specialty obstetric anesthesiologists. Then, by intensification of obstetric anesthesiology manpower development, coupled with regionalization of maternal care, all centers delivering complex maternity care could provide 24/7 availability of maternity rescue-ready clinicians, on-site, where most “potentially avoidable” obstetrical-related catastrophes occur.
Name: Peter G. Pryde, MD.
Contribution: This author conceived and wrote the entire manuscript. There are no original data presented, but an extensive analysis and interpretation of previous relevant published work. He provided final approval of the version to be published and agrees to be accountable for all aspects of the work.
This manuscript was handled by: Jill M. Mhyre, MD.
1. Manning FAReflections on future directions of perinatal medicine. Semin Perinatol. 1989;13:342–351.
2. Mandel DC, Pryde PG, Shah DM, Iruretagoyena JIUse of Doppler ultrasound in the management of uteroplacental perfusion during cardiopulmonary bypass in pregnancy. Int J Obstet Anesth. 2016;27:75–80.
3. Mattingly SSThe maternal-fetal dyad. Exploring the two-patient obstetric model. Hastings Cent Rep. 1992;22:13–18.
4. Chervenak FA, McCullough LBThe fetus as a patient: an essential ethical concept for maternal-fetal medicine. J Matern Fetal Med. 1996;5:115–119.
5. D’Alton MEWhere is the “M” in maternal-fetal medicine? Obstet Gynecol. 2010;116:1401–1404.
6. Chang J, Elam-Evans LD, Berg CJ, et alPregnancy-related mortality surveillance–United States, 1991–1999. MMWR Surveill Summ. 2003;52:1–8.
8. GBD 2015 Maternal Mortality Collaborators. Global, regional, and national levels of maternal mortality, 1990–2015: a systematic analysis for the Global Burden of Disease Study 2015. Lancet. 2016;388:1775–1812.
9. Creanga AA, Berg CJ, Ko JY, et alMaternal mortality and morbidity in the United States: where are we now? J Womens Health (Larchmt). 2014;23:3–9.
10. Agrawal PMaternal mortality and morbidity in the United States of America. Bull World Health Organ. 2015;93:135.
11. Global Burden of Disease Health Financing Collaborator Network. Evolution and patterns of global health financing 1995–2014: development assistance for health, and government, prepaid private, and out-of-pocket health spending in 184 countries. Lancet. 2017;389:1981–2004.
12. Mathews TJ, Hamilton BEMean age of mothers is on the rise: United States, 2000–2014. 2016.Hyattsville, MD: National Center for Health Statistics; NCHS Data Brief, No. 232.
13. Moussa HN, Alrais MA, Leon MG, Abbas EL, Sibai BMObesity epidemic: impact from preconception to postpartum. Future Sci OA. 2016;2:FSO137.
14. Louis JM, Menard MK, Gee RERacial and ethnic disparities in maternal morbidity and mortality. Obstet Gynecol. 2015;125:690–694.
15. Main EK, McCain CL, Morton CH, Holtby S, Lawton ESPregnancy-related mortality in California: causes, characteristics, and improvement opportunities. Obstet Gynecol. 2015;125:938–947.
16. Mhyre JM, Bateman BTStemming the tide of obstetric morbidity: an opportunity for the anesthesiologist to embrace the role of peridelivery physician. Anesthesiology. 2015;123:986–989.
17. Silber JH, Williams SV, Krakauer H, Schwartz JSHospital and patient characteristics associated with death after surgery. A study of adverse occurrence and failure to rescue. Med Care. 1992;30:615–629.
20. California Maternal Quality Care Collaborative. California Maternal Quality Care Collaborative Quality Initiatives. Available at: https://www.cmqcc.org/qi-initiatives
. Accessed June 30, 2017.
21. MacDorman MF, Declercq E, Cabral H, Morton CRecent increases in the US maternal mortality rate: disentangling trends from measurement issues. Obstet Gynecol. 2016;128:447–455.
22. Main EK, Cape V, Abreo A, et alReduction of severe maternal morbidity from hemorrhage using a state perinatal quality collaborative. Am J Obstet Gynecol. 2017;216:298.e1–298.e11.
23. D’Alton ME, Bonanno CA, Berkowitz RL, et alPutting the “M” back in maternal-fetal medicine. Am J Obstet Gynecol. 2013;208:442–448.
24. Wenstrom K, Erickson K, Schulkin JAre obstetrician-gynecologists satisfied with their maternal-fetal medicine consultants? A survey. Am J Perinatol. 2012;29:599–608.
25. American College of Obstetricians and Gynecologists' Committee on Patient Safety and Quality Improvement; American College of Obstetricians and Gynecologists' Committee on Obstetric Practice. Committee Opinion No. 657 Summary: The Obstetric and Gynecologic Hospitalist. Obstet Gynecol. 2016;127:419.
26. Stevens TA, Swaim LS, Clark SLThe role of obstetrics/gynecology hospitalists in reducing maternal mortality. Obstet Gynecol Clin North Am. 2015;42:463–475.
27. Levine LD, Schulkin J, Mercer BM, O’Keeffe D, Berghella V, Garite TJRole of the hospitalist and maternal fetal medicine physician in obstetrical inpatient care. Am J Perinatol. 2016;33:123–129.
28. Birnbach DJ, Bucklin BA, Dexter FImpact of anesthesiologists on the incidence of vaginal birth after cesarean in the United States: role of anesthesia availability, productivity, guidelines, and patient safety. Semin Perinatol. 2010;34:318–324.
29. Menard MK, Kilpatrick S, Saade G, et alLevels of maternal care. Am J Obstet Gynecol. 2015;212:259–271.
30. D’Alton ME, Main EK, Menard MK, Levy BSThe national partnership for maternal safety. Obstet Gynecol. 2014;123:973–977.
31. Moaddab A, Dildy GA, Brown HL, et alHealth care disparity and state-specific pregnancy-related mortality in the United States, 2005-2014. Obstet Gynecol. 2016;128:869–875.