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Race matters: maternal morbidity in the Military Health System

Published:March 06, 2021DOI:https://doi.org/10.1016/j.ajog.2021.02.036

      Background

      In the United States, Black women are 3 to 4 times more likely to die from childbirth and have a 2-fold greater risk of maternal morbidity than their White counterparts. This disparity is theorized to be related to differences in access to healthcare or socioeconomic status. Military service members and their dependents are a diverse community and have equal access to healthcare and similar socioeconomic statuses.

      Objective

      This study hypothesized that universal access to healthcare, as seen in the military healthcare system, leads to similar rates of maternal morbidity regardless of race or ethnic background.

      Study Design

      A retrospective cohort study included data from the inaugural National Perinatal Information Center special report comparing indicators of severe maternal morbidity by race. National Perinatal Information Center data from participating military treatment facilities in the Department of Defense performing more than 1000 deliveries annually from April 1, 2018, to March 31, 2019, were included. Using this convenience data set, Chi-square analyses comparing the percentages of cesarean deliveries, adult intensive care unit admissions, and severe maternal morbidity between Black and White patients were performed.

      Results

      Black women were more likely to deliver via cesarean delivery (31.68% vs 23.58%; P<.0001; odds ratio, 1.5; 95% confidence interval, 1.38–1.63), be admitted to an adult intensive care unit (0.49% vs 0.18%; P=.0026; odds ratio, 2.78; 95% confidence interval, 1.46–5.27), and experience overall severe maternal morbidity (2.66% vs 1.66%; P=.0001; odds ratio, 1.67; 95% confidence interval, 1.3–2.15) even when excluding blood transfusion (0.64% vs 0.32%; P=.0139; odds ratio, 1.99; 95% confidence interval, 1.17–3.36) than their White counterparts. There were no substantial differences between races in overall severe maternal morbidity associated with postpartum hemorrhage even when excluding blood transfusion in this subset.

      Conclusion

      Equal access to healthcare and similar socioeconomic statuses in the military healthcare system do not explain the healthcare disparities seen regarding maternal morbidity encountered by Black women having children in the United States. This study identifies healthcare disparities in severe maternal morbidity among active duty service members and their families. Further studies to assess causes such as systemic racism (including implicit and explicit medical biases) and physiological factors are warranted.

      Key words

      Introduction

      Maternal morbidity and mortality are on the rise in the United States despite continued advancements in the field of medicine. Compared with other developed countries, women in the United States have a 2 to 4 times greater chance of death associated with pregnancy and childbirth.
      World Health Organization
      Trends in maternal mortality 2000 to 2017: estimates by WHO, UNICEF, UNFPA, World Bank Group and the United Nations Population Division.
      Maternal mortality rates have risen in the United States to a rate of 17.4 deaths to 100,000 live births in 2018.
      Centers for Disease Control and Prevention
      Maternal mortality. National Center for Health Statistics.
      Black women are 3 to 4 times more likely to die from childbirth and experience a 2-fold greater risk of maternal morbidity than their White counterparts.
      Centers for Disease Control and Prevention
      Maternal mortality. National Center for Health Statistics.
      For every maternal death, approximately 100 women experience significant morbidity, equaling somewhere around 60,000 women in the United States experiencing morbidity surrounding childbirth annually.
      • Callaghan W.M.
      • Creanga A.A.
      • Kuklina E.V.
      Severe maternal morbidity among delivery and postpartum hospitalizations in the United States.
      Despite representing only half of all births in the United States, minorities are disproportionately affected by this trend which has significant implications for this vulnerable population.
      • Leonard S.A.
      • Main E.K.
      • Scott K.A.
      • Profit J.
      • Carmichael S.L.
      Racial and ethnic disparities in severe maternal morbidity prevalence and trends.
      The root cause of this healthcare disparity has been the subject of much research and debate and is thought to be related to multiple social determinants of health.

      Why was this study conducted?

      This study aimed to determine the presence of racial disparities among indicators of severe maternal morbidity (SMM) in the military healthcare system.

      Key findings

      Black women are more likely to be admitted to an adult intensive care unit, deliver via cesarean delivery, and experience overall SMM (even when excluding blood transfusion) than their White counterparts despite equal access to healthcare and similar socioeconomic statuses in the military healthcare system.

      What does this add to what is known?

      There have been many studies performed in the privatized United States healthcare system to identify morbidity and mortality associated with maternal racial disparities. The military healthcare system offers a unique paradigm to determine whether similar rates of maternal racial disparities exist in a system of universal healthcare coverage seen in other developed countries.
      Committee on Health Care for Underserved Women
      ACOG Committee Opinion No. 729: importance of social determinants of health and cultural awareness in the delivery of reproductive health care.
      ACOG Committee Opinion No. 649: racial and ethnic disparities in obstetrics and gynecology.
      • Bryant A.S.
      • Worjoloh A.
      • Caughey A.B.
      • Washington A.E.
      Racial/ethnic disparities in obstetric outcomes and care: prevalence and determinants.
      • Grobman W.A.
      • Parker C.B.
      • Willinger M.
      • et al.
      Racial disparities in adverse pregnancy outcomes and psychosocial stress.
      In the United States Military, service members and their families are granted equal access to healthcare through universal insurance coverage creating a unique paradigm for study on equity in this healthcare system. Despite this fact, there is a paucity of available research investigating the presence of healthcare disparities in the United States Military medical system. Retirees, active duty service members, and dependents, including spouses and children up to the age of 23 years (if in school), are granted access to government-sponsored health insurance plans (Tricare) mandated by the Affordable Care Act without risk of denial for coverage based on preexisting medical conditions or if they develop major medical illness during period of coverage. These patients receive care at military treatment facilities (MTFs) or in the civilian sector if no maternity services are available at their duty station.

      Materials and Methods

      This retrospective cohort study included clinical data collected from April 1, 2018, to March 31, 2019, as a part of the inaugural special report on maternal metrics by race released by the National Perinatal Information Center (NPIC) in July 2019. NPIC is a nonprofit, voluntary, multistate perinatal data repository representing more than 725,000 perinatal discharges each year, providing participants with comparative data to national benchmarks for perinatal outcomes.
      National Perinatal Information Center
      Informing change in perinatal outcomes.
      A total of 41 MTFs who perform inpatient obstetrical care participate in NPIC as a part of continuous quality improvement initiatives. We reviewed the NPIC special data report from 13 MTFs performing more than 1000 deliveries per year including Navy Medical Center San Diego (San Diego, CA), Naval Medical Center Portsmouth (Portsmouth, VA), Womack Army Medical Center (Fort Bragg, NC), Tripler Army Medical Center (Honolulu, HI), William Beaumont Army Medical Center (Fort Bliss, TX), Naval Medical Center Camp Lejeune (Camp Lejeune, NC), Blanchfield Army Community Hospital (Fort Campbell, KY), Evans Army Community Hospital (Fort Carson, CO), Carl R. Darnall Army Medical Center (Fort Hood, TX), Naval Hospital Camp Pendleton (Camp Pendleton, CA), Brooke Army Medical Center (Join Base San Antonio, TX), Fort Belvoir Community Hospital (Fort Belvoir, VA), and Walter Reed National Military Medical Center (Bethesda, MD). These 13 MTFs are considered “high volume” hospitals and as such provide similar services in terms of intensive care unit (ICU) treatment, Maternal-Fetal Medicine consultation, and Neonatal ICU coverage. Kozhimannil et al
      • Kozhimannil K.B.
      • Thao V.
      • Hung P.
      • Tilden E.
      • Caughey A.B.
      • Snowden J.M.
      Association between hospital birth volume and maternal morbidity among low-risk pregnancies in rural, urban, and teaching hospitals in the United States.
      found associations between hospital volume and maternal morbidity, using 1000 deliveries per year as the cutoff between low- and high-volume hospitals. Approval for analytical review was obtained from Brooke Army Medical Center Institutional Review Board.
      This convenience data set included a wide range of primarily teaching hospitals (12 of 13 locations training Obstetrics and Gynecology and/or Family Medicine residents) across all branches of military service allowing for comparisons between MTFs and relative to national perinatal outcomes. Patients included in the study were retirees, active duty service members, and dependent spouses or children who have access to government-sponsored health insurance plans (Tricare). The primary outcomes of interest were rates of cesarean deliveries, adult ICU admission, and severe maternal morbidity (SMM) relative to maternal race. Self-identified races in the NPIC data collection included White, Black, Asian or Pacific Islander, Western Hemisphere Indians, other, and unknown. Given the low overall numbers of women identifying as Asian/Pacific Islander and Western Hemisphere Indians and high rates of unknown or other race, we opted to limit our comparison to Black and White women, also allowing for a binomial distribution for statistical comparison.
      A patient was determined to experience SMM based on guidelines from Centers for Disease Control and Prevention (CDC) on the 21 indicators of SMM and their corresponding tenth revision of the International Classification of Diseases, Tenth Revision (ICD-10) codes used during delivery hospitalization.
      Centers for Disease Control and Prevention. Reproductive Health
      How does CDC identify severe maternal morbidity?.
      Postpartum hemorrhage was defined as estimated blood loss greater than 1000 mL after delivery. Up to half of SMM is caused by the utilization of blood transfusion alone.
      • Leonard S.A.
      • Main E.K.
      • Scott K.A.
      • Profit J.
      • Carmichael S.L.
      Racial and ethnic disparities in severe maternal morbidity prevalence and trends.
      By evaluating SMM with the inclusion and exclusion of blood transfusion, we can remove the bias of blood transfusion only which may include patients with preexisting anemia or less severe disease. We included cesarean deliveries in our review because the proportion of women experiencing SMM is higher among women who undergo cesarean delivery and cesarean delivery has been shown to contribute to worse maternal outcomes.
      • Leonard S.A.
      • Main E.K.
      • Scott K.A.
      • Profit J.
      • Carmichael S.L.
      Racial and ethnic disparities in severe maternal morbidity prevalence and trends.
      The rates of SMM were summarized using counts and percentage per 1000 annual deliveries, and chi-square analysis was used to compare across race. Odds ratios (ORs) and their corresponding 95% confidence intervals (CIs) were also calculated. Statistical significance was identified as P<.05. All analyses were performed using JMP 13.2 (SAS Corp, Cary, NC).

      Results

      The NPIC data included in our convenience data set are represented in Figure 1. Comparisons between sites to determine whether there was a statistically significant difference in the rate of occurrence of SMM per 1000 deliveries were not performed owing to inadequate sample sizes necessary for statistical tests. During the period of data collection, the MTFs included in the analysis had a total of 23,728 deliveries with 15,305 encompassing self-identified Black and White women. Notably, 23% of the deliveries were identified as Black and 77% were identified as White. The overall rate of cesarean deliveries at these institutions ranged from 19.4% to 35.5%. A total of 282 women experienced SMM including 38 adult ICU admissions and 190 postpartum hemorrhages. Baseline demographic characteristics or clinical histories of patients included in this study were not available for comparison in this deidentified, aggregate dataset from NPIC.
      Figure thumbnail gr1
      Figure 1SMM rates across 13 military treatment facilities
      Rates per 1000 deliveries between Black and White women at 13 sites in the Military Health System.
      ICU, intensive care unit; SMM, severe maternal morbidity.
      Hamilton et al. Maternal racial disparities in the Military Health System. Am J Obstet Gynecol 2021.
      There was a statistically significant difference noted between Black and White patients in several of our outcomes of interest. Black women were more likely to deliver via cesarean delivery (31.68% vs 23.58%; P<.0001; OR, 1.5; 95% CI, 1.38–1.63), be admitted to an adult ICU (0.49% vs 0.18%; P=.0026; OR, 2.78; 95% CI, 1.46–5.27), and experience overall SMM (2.66% vs 1.66%; P=.0001; OR, 1.67; 95% CI, 1.3–2.15) even when excluding blood transfusion (0.64% vs 0.32%; P=.0139; OR, 1.99; 95% CI, 1.17–3.36) than their White counterparts (Figures 2 and 3). There were no significant differences between races in overall SMM associated with postpartum hemorrhage (30.63% vs 35.46%; P=.2851; OR, 1.24; 95% CI, 0.84–1.85) even when excluding blood transfusion (4.37% vs 5.59%; P=.5512; OR, 1.3; 95% CI, 0.56–3.01) in this subset (Figure 4).
      Figure thumbnail gr2
      Figure 2Cesarean delivery rates by race
      Overall rate of cesarean delivery per 1000 deliveries seen in all 13 sites when comparing Black and White women (the asterisk indicates P<.05).
      Hamilton et al. Maternal racial disparities in the Military Health System. Am J Obstet Gynecol 2021.
      Figure thumbnail gr3
      Figure 3SMM by race
      Rates of SMM per 1000 deliveries seen in all 13 sites when comparing Black and White women for adult ICU admission, SMM when excluding blood transfusion, and overall SMM (the asterisk indicates P<.05).
      ICU, intensive care unit; SMM, severe maternal morbidity.
      Hamilton et al. Maternal racial disparities in the Military Health System. Am J Obstet Gynecol 2021.
      Figure thumbnail gr4
      Figure 4SMM in postpartum hemorrhage cases by race
      Rates of SMM per 1000 deliveries involving postpartum hemorrhage seen in all 13 sites when comparing Black and White women (the asterisk indicates P<.05).
      SMM, severe maternal morbidity.
      Hamilton et al. Maternal racial disparities in the Military Health System. Am J Obstet Gynecol 2021.

      Comment

      Principal findings

      We hypothesized that given universal access to healthcare among active duty service members and their families, there would be similar rates of maternal morbidity regardless of race. However, we identified significant disparity between Black and White women among rates of cesarean delivery, adult ICU admission, and SMM within our MTFs. The rates of SMM among postpartum hemorrhage cases between races were not statistically significant. Hemorrhage was observed in 3.56% of deliveries among Black women and 3.06% of deliveries among White women. This nonstatistical difference was likely caused by an overall small number of reported cases but available data suggest a concerning trend toward higher rates in Black women.

      Results

      Despite universal access to healthcare in the military healthcare system, our results affirm the presence of disparities in maternal outcomes for Black women in the United States. These findings were surprising given that the driving theories behind the maternal race disparities encountered in this country include access to care and socioeconomic status, both of which have effectively been controlled for in our data set. All except 1 MTF had cesarean delivery rates less than the United States national rate of 31.9% determined by the CDC in 2018.
      Centers for Disease Control and Prevention. Reproductive Health
      How does CDC identify severe maternal morbidity?.
      SMM rates, both overall and when excluding blood transfusion, in the Military Health System are similar to national trends reported most recently by the CDC in 2014.
      • Martin J.A.
      • Hamilton B.E.
      • Osterman M.J.K.
      • Driscoll A.K.
      Births: final data for 2018.
      The overall SMM during the study period was 2% and 0.5% when excluding blood transfusions compared with 1.4% and 0.35% in 2014.

      Clinical implications

      Our findings indicate that there are likely other factors at play which impact the obstetrical outcomes of women based on their race. These may be systems-based barriers to accessing the military healthcare system which contribute to healthcare disparities or they may be rooted in systemic or implicit biases which occur within our healthcare delivery. Further investigation must be done to try to identify these causes of maternal disparities within both the military population and the larger maternal population in the United States. In addition, these findings show that, even in a universal healthcare system, we still have work to do to level the playing field for all of our obstetrical patients and process improvement initiatives to work to improve racial disparities in our military population are valid and warranted.

      Research implications

      Additional studies on the presence of healthcare disparities in the Military Health System are necessary to further investigate our findings. For instance, differences in pay scales among Enlisted and Officer service members may ultimately create socioeconomic disparities not as readily identified as in the civilian sector. The most recently available demographic data on the active duty component of the United States Military would further support this claim, showing a higher proportion of Black Enlisted service members than Black Officers (19% vs 9% respectively) compared with their White counterparts (67% vs 77%, respectively).
      Department of Defense (DoD)
      Office of the Deputy Assistant Secretary of Defense for Military Community and Family Policy (ODASD (MC&FP)). 2018 Demographics report. Profile of the Military Community.
      Our current data set is not stratified by Service Member rank, therefore precluding us from answering this question in the current study.
      Investigation into potential differences among those accessing care (ie, compliance with routine prenatal visit and laboratory evaluation, postpartum follow-up) might identify barriers to care despite universal insurance coverage in our patient population. Finally, our data do not include information on any maternal conditions that might predispose to SMM such as maternal age, obesity, or other preexisting conditions.

      Strengths and limitations

      A strength of our study is that it includes data reported from MTFs across the United States and 3 military branches of service (Air Force, Army, and Navy) providing a more robust external validity to our results. In addition, NPIC data are validated before inclusion and rely on trained research personnel to extract data, not simply relying on ICD-10 codes alone. With a paucity of studies looking at racial disparities in the Military Health System, this study adds to the national dialog and the need to address systemic racism.
      Our study has a few limitations. First, there are limitations with the convenience data set provided by NPIC. Of note, 61% of patients self-reported race as “other” reflecting the growing homogeneity of American society and culture making accurate comparisons between races more difficult. In addition, owing to the deidentified nature of the data set, we were unable to compare baseline characteristics or clinical histories of patients included in the study. Second, we were unable to determine rates of SMM related to preeclampsia, a common cause of maternal morbidity and mortality worldwide, because we were unable obtain the total denominator to allow for statistical analysis in this convenience data set. Third, our study design is limited in that we only include high volume MTFs providing full scope obstetrical services in our analysis, opting to exclude low volume hospitals where more complex patients may be transferred to a higher level of care. However, most of the MTFs included serve as teaching hospitals and referral centers for smaller MTFs across the Department of Defense and may see a greater proportion of higher acuity patients which could skew outcomes. Future studies could be undertaken with a more comprehensive data set which would address the abovementioned limitations and examine all of the obstetrical care provided to our patients including that within our MTFs and the care obtained through civilian providers (care purchased by Tricare when MTF care is not available).

      Conclusions

      Further studies to assess causes of these identified healthcare disparities concerning maternal morbidity, such as systemic racism (including implicit and explicit medical biases) and physiological factors, are warranted. The implication of disparities identified in SMM for service members could be considered a matter of national security and as such deserves special attention.

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        • Committee on Health Care for Underserved Women
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      1. ACOG Committee Opinion No. 649: racial and ethnic disparities in obstetrics and gynecology.
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