The Impact of Racial Inequities on the Burden of Adverse Maternal Outcomes in the United States

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Drawing of a pregnant women on a white background with stick figure drawings on the background

Illustration by Nikitha Bhimireddy

Article by Mallory Go

 

Introduction

The high prevalence of preventable maternal deaths in the United States (US) is a tragedy. The US is an alarming outlier due to higher health expenditures and maternal mortality rates (MMR) than comparable countries such as Canada, France, and Germany. The US MMR has increased despite spending significantly more per individual on health than the Organization for Economic Co-operation and Development (OECD) average.1 Furthermore, high rates of maternal mortality—death due to pregnancy-related complications—and maternal morbidity—any adverse condition caused or aggravated by pregnancy—are both avoidable and influenced by disparities, such as racial and ethnic inequities.2 The persistence of racial and ethnic inequities in healthcare has led to increased maternal mortality and morbidity among certain populations. A patient’s racial/ethnic identity can lead to differences in access to contraceptive care, prenatal care utilization, hospital care, pregnancy-related complications, and adverse health outcomes. On top of that, persistent racial/ethnic inequities negatively impact patients’ access to care and have led to significant disparities in minority maternal health outcomes compared to their white counterparts.3 While maternal mortality has decreased on a global scale, maternal mortality in the U.S. has increased despite being a high-income country.1 In 2000 to 2020, while the global maternal mortality rate decreased by approximately 50%, the U.S. maternal mortality rate increased by approximately 30% from 2000 to 2014.1,2,4 This concerning trend is exacerbated by the disproportionate amount of adverse maternal and perinatal health outcomes experienced by Black individuals.3 This paper will examine disparities in conditions that are epidemiologically correlated with adverse maternal and perinatal outcomes among Black individuals and the potential mechanisms behind these disparities. The conditions of concern are (1) obstetric hemorrhage; (2) preeclampsia and eclampsia; (3) cardiovascular events and cardiomyopathy; and (4) indirect causes and chronic conditions. This paper aims to synthesize current research regarding the specific causes, identify limitations and strengths of current research, and recommend areas of improvement based on the literature. To create a more comprehensive review of the disparity, the paper will highlight how social determinants of health impact health disparities.

 

Methods

The focus of this paper is adverse health outcomes in the Black maternal population in the U.S. through synthesizing studies conducted solely in the U.S.. Historically, race has been considered a biological category rather than a social concept related to cultural, political, and economic risk factors. However, for this literature review, race will be operationalized as a social risk factor with associated adverse health outcomes rather than a biological risk factor.5 The participants of interest are referred to as “African Americans”, “Black Individuals”, “Black mothers”, and “Black patients” in the reviewed studies. Throughout this paper, for the purpose of inclusivity, they will be referred to as “Black Individuals.” While thousands of studies were found relating to maternal mortality and racial disparities, only 10 studies were selected for inclusion and discussion in this review based on the primary data source, location, data on specific conditions, assessment of bias, comparison involving Black women, and relevance to disparate outcomes.

 

Direct causes of obstetric death

According to the World Health Organization (WHO), direct causes of obstetric death are conditions that result from complications of the pregnant state and the interventions, or lack thereof, resulting from those complications.4

Obstetric Hemorrhage

Obstetric hemorrhage, including postpartum hemorrhage (PPH), is defined as abnormal uterine bleeding where 500mL of blood after vaginal delivery or 1000mL of blood after a cesarean section is lost.6

Research Methodology and Findings

A retrospective cohort study examining how race is associated with adverse maternal health outcomes relating to PPH found that Black Individuals were at a significantly higher risk of severe morbidity and mortality from PPH.7 Data from the largest publicly available inpatient database, the National Inpatient Sample (NIS), was used for this study. The primary exposure evaluated was maternal race, and the primary outcome was severe maternal morbidity. The study also evaluated PPH-related measures such as death, hysterectomy, and disseminated intravascular coagulation to increase the robustness of the analysis. The study minimized missing data and bias by utilizing the NIS instead of the Healthcare Cost and Utilization Project State Inpatient Database. In 2007, another retrospective study analyzed data from the U.S. National Hospital Discharge Survey (NHDS), U.S. National Vital Statistics System, and the CDC Pregnancy Mortality Surveillance System to determine hemorrhage prevalence and case-fatality rates for Black and white women.8

According to Gyamfi-Bannerman et al., non-Hispanic Black Individuals were at a 24-28% higher risk for severe maternal morbidity compared to non-Hispanic white women. The study also found that Black Individuals were at approximately five times greater risk for death.7 Similarly, the Tucker et al. study explored the disparity of increased risk of pregnancy-related mortality among Black Individuals, finding that Black Individuals did not have a significantly greater prevalence of postpartum hemorrhage than white women. However, Black Individuals experienced higher pregnancy-related mortality due to a 3.3 times higher case fatality rate as compared to white women.8

Limitations and Strengths

With regard to the Gyamfi-Bannerman et al. study, the database used contains approximately 20% of hospitalizations nationally. The data set did not provide information regarding hospital resources, protocols, and staffing. Estimated blood loss measurements were also unavailable. The study was also limited in the quantifying of maternal burden in regard to PPH. For example, the degree that the maternal outcome of PPH may be associated with underlying comorbidities, or multiple medical conditions, was not explored.7 Approximately 21% of NHDS records used in the Tucker et al. study did not specify race. The study assigned records with unknown race as white, after analyzing the hospitals that contributed the incomplete records were located in areas of a predominantly white population. According to the data analysis of the study, this assumption did not significantly impact the findings. Although this assumption seems valid due to the demographic data on the location of the incomplete records, there is still potential for error. The study was not able to measure the extent patient characteristics, such as comorbidities, prenatal care utilization, and disease severity, and social determinants of health such as access to quality care and insurance status contributed to the increased case-fatality rates among Black Individuals.8

 

Preeclampsia/Eclampsia

Hypertensive disorders of pregnancy are among the most preventable causes of maternal mortality. The most common and severe disorders are preeclampsia and eclampsia.9

Research Methodology and Findings

A retrospective cohort study utilized National Inpatient Sample (NIS) data to assess the association between race and adverse outcomes relating to preeclampsia. The primary exposure evaluated was maternal race and the primary outcome was severe maternal morbidity due to preeclampsia. The risk for maternal in-hospital mortality for women with preeclampsia was also evaluated.3 A similar study by Shahul et al. was conducted using NIS data from 2004-2012, observing the same primary exposure of patient race and the primary outcome was inpatient mortality during hospitalization. The study looked at potential mechanisms and risk factors in Black individuals that led to adverse health outcomes.9 Gad et al. also recently used NIS data to evaluate the risk of adverse maternal health outcomes for Black Individuals with pregnancy-induced hypertension. The study observed outcomes and specific comorbidities associated with hypertension, along with hospital region, length of stay, primary payer, median regional income, and insurance status (which was used as a proxy for healthcare access).10

The MacDorman et al. study found that Black Individuals are at a higher risk for severe morbidity and mortality due to preeclampsia. Regarding other morbidity diagnoses, non-Hispanic Black Individuals were at a higher risk for stroke, pulmonary edema, renal failure, and eclampsia compared to other races. The risk for maternal in-hospital deaths for non-Hispanic Black Individuals was 48.9 per 100,000 deliveries. This is significantly higher than the risk for non-Black Individuals of 14.8 per 100,000 deliveries.3 The Shahul et al. study results suggest that Black Individuals are more likely to have comorbidities such as hypertension, diabetes, and obesity. Black Individuals with preeclampsia had higher rates of maternal and fetal complications and maternal mortality when compared with white women.9 The Gad et al. study concluded that pregnancy-induced hypertension disorders such as preeclampsia and eclampsia are associated with acute cardiovascular complications such as heart failure and peripartum cardiomyopathy. Black Individuals had the highest in-hospital mortality with an adjusted odds ratio for comorbidities, socioeconomic status, and healthcare access of 1.45 compared to white and Hispanic women. Pacific Islander/Asian women are the only observed race category with a higher adjusted odds ratio of 2.00.10

Limitations and Strengths

The MacDorman et al. study was not able to determine if the complication occurred before hospital admission or developed during hospitalization. Another important limitation was that the study used data before the recommendation of aspirin use for preeclampsia prevention: data from post-recommendation years may lead to different results despite adjustments for comorbidities such as maternal age and hypertensive diagnoses in the analysis.3 One strength of the Shahul et al. study is in its adjustment for potential confounding variables such as age, gestation time, delivery type, maternal comorbidities, and socioeconomic status.9 The Gad et al. study came with limitations associated with retrospective studies such as database coding errors and vulnerability to misclassification bias. The study acknowledged that the NIS database lacked patient demographics such as education level, medications, peripartum follow-up, and readmission. However, the study found that disparities persist despite adjusted comorbidities, socioeconomic status, and access to healthcare.10

 

Cardiovascular Events and Cardiomyopathy

Cardiomyopathy in pregnancy can be categorized into two groups: peripartum cardiomyopathy (PPCM) and “other cardiomyopathy”.11

Research Methodology and Findings

A retrospective analysis study by Goland et al. from the University of Southern California and Louisiana State University Health Science Center compared the difference in the clinical profiles of Black Individuals with PPCM and white patients with PPCM and the consequential outcomes.12 A similar retrospective study was performed by Whitehead using data from the CDC Pregnancy Mortality Surveillance System that examined pregnancy-related deaths due to cardiomyopathy from 1991-1997.11 The findings of a third retrospective study investigated potential explanations for the racial disparities in cardiovascular events. This study also used the NIS database and analyzed pregnancy or postpartum-related hospitalizations. Patient demographics and medical/pregnancy-related comorbidities were identified, and hospital-related characteristics were compared between different races/ethnicities.10

According to the Goland et al. retrospective analysis study, Black Individuals with PPCM had a higher rate of mortality than white patients with PPCM, at 11.5% and 4.8%, respectively. The analysis also indicated a higher incidence of complications and adverse outcomes in Black Individuals compared to white patients.12 The Whitehead retrospective study found that Black Individuals were 6.4 times as likely to die from cardiomyopathy as white women. This cause-specific pregnancy-related mortality disparity is larger than that for any other cause of death. Among patients in both cardiomyopathy groups, 22% had preeclampsia or pregnancy-induced hypertension and 6% had a pulmonary or cerebrovascular embolism.11 The Gad study concluded that risk factors associated with adverse pregnancy outcomes are more prevalent in Black Individuals than in white women. As a specific example, the prevalence of cardiovascular disease and obesity is greater in Black Individuals compared to white women, which may be attributable to an increased risk of poor dietary habits due to the increased likelihood of being low-income and having restricted access to affordable, nutritional foods. Black Individuals exhibited a higher risk of in-hospital mortality, acute myocardial infarction, stroke, pulmonary embolism, and PPCM compared to white patients, with odds ratios of 1.45, 1.23, 1.57, 1.42, and 1.71, respectively. Racial disparities persist despite adjustments regarding education, socioeconomic factors, and healthcare access. These results indicate disparities specifically within healthcare quality and care experience. This is supported by the difference in healthcare coverage: most Black pregnant women were insured by Medicaid and earned below-median income compared with white pregnant women who mainly had private insurance and earned above-median income.10

Limitations and Strengths

The Goland et al. study relied on patient records and physician reports. Therefore, the data may be subject to reporting biases such as underreporting. While the study could not explain the racial disparities observed, it did provide data from the largest group of patients with PPCM.12 The Whitehead retrospective study was conducted using data before the revision of the death certificate to include the pregnancy status checkbox. This may have led to an underreporting of pregnancy-related deaths due to cardiomyopathy.11 The Gad study had inherent design limitations as a retrospective study. Additionally, the NIS database used by the Gad study does not include further patient demographic or follow-up, post-hospitalization information.10

 

Indirect Causes of Obstetric Death

According to the WHO, indirect causes of obstetric deaths are preexisting conditions or conditions that developed during pregnancy and were aggravated by pregnancy.1

Research Methodology and Findings

In a retrospective study examining trends and disparities in US maternal mortality, Singh and Lee aimed to understand the correlation between indirect obstetric causes and chronic conditions by maternal race, residence, immigrant, marital, and socioeconomic status. The study used data from the National Vital Statistics System and area-based socioeconomic data from county-level censuses and data from the American Community Survey.13 In another retrospective study by Singh et al., birth certificate data from the CDC’s National Center for Health Statistics from 2014-2015 was used to examine sociodemographic variations and disparities in maternal hypertension.14 Singh and Lee found that maternal mortality from indirect causes was 2-3 times greater among Black Individuals than among white women. While maternal mortality from indirect causes increased for the overall population, there was still a significant disparity between Black Individuals and white patients–maternal mortality was significantly greater for all chronic conditions among Black Individuals than among white women, except for mental health conditions.13 In the data from the Singh et al. study, Black Individuals of all ages had the highest prevalence of maternal hypertension at 9.8%. Also, regarding sociodemographic and medical conditions associated with maternal hypertension, Black Individuals had the greatest prevalence of pre-pregnancy overweight and obesity status, at 61.8%, and 35.0%, respectively. The maternal mortality rate associated with chronic conditions, including cardiovascular disease, was approximately two times greater among Black Individuals compared to white women.14

Limitations and Strengths

Since the data used in the Singh and Lee study was taken from two unlinked data sources, researchers were unable to conduct individual-level analyses that may have more accurately explained severe maternal morbidity outcomes that impact maternal mortality. The study also acknowledged potential inconsistencies in the reporting of race and ethnicity, sociodemographic factors, and maternal deaths. For example, the varied adoption of the pregnancy checkbox on the death certificate may have influenced the classification of maternal deaths associated with indirect causes.13 The main strength of the Singh et al. study was its large sample size of 8 million women and diverse subgroup comparisons. However, the study was not able to fully explain the variations and disparities observed in maternal hypertension due to the lack of data on other hypertensive risk factors such as diet, socioeconomic status, and family history. Similarly, the study was not able to distinguish between different hypertensive disorders such as preeclampsia and eclampsia, and it also acknowledged that there may have been underreporting of gestational hypertension for women who did not receive timely, consistent prenatal care.14

 

Conclusion

All of the studies reviewed in this paper were retrospective studies and therefore had limitations intrinsic to retrospective studies such as missing data, inconsistency in data reporting, and selection bias. While retrospective studies can determine association, they cannot determine causation.15 The majority of studies reviewed in this paper acknowledged that understanding the complex interactions between social determinants, contextual factors, and racial disparities in maternal and perinatal outcomes is beyond their scope.

Social determinants of health (SDOH) are conditions and factors that impact risks, quality of life, and health outcomes.16 Structural and institutional inequalities have likely exacerbated this health disparity. According to a survey by Lillie-Blanton et al., Black Individuals report greater difficulty than white patients in receiving consistent care and report higher rates of mistreatment during pregnancy.17 Black Individuals are more likely to be covered by Medicaid or other public insurance than their white counterparts and are approximately twice as likely to be uninsured.18 Due to the limitations of public insurance like Medicaid, patients often have restricted options in terms of healthcare.17 This can result in the three major categories of delay of care that lead to maternal mortality and morbidity: delay to seek care, delay of access, and delay of provision.16 The utilization of prenatal care, a significant protective factor against adverse maternal and perinatal outcomes, is a prime example of delay of care: Black Individuals are more likely to receive prenatal care late or not at all. Gadson predicts that this may be due to a variety of factors such as fear and mistrust of medical procedures or providers, perceived discrimination, low socioeconomic status, insurance status, and lack of social support. These determinants are often interconnected and can occur at a population or individual level.16

Primary examples of stress factors that Black Individuals are more likely to experience include living in economically deprived neighborhoods with less access to quality healthcare and social services and higher rates of crime and violence. Increased psychosocial stress and low social support are associated with smoking and substance use in low-income pregnant Black Individuals.19 External stressors and detrimental coping mechanisms in response to the stressors can adversely affect preconception and pregnancy health.20 The “weathering hypothesis” is a theory that the allostatic load of stress on physiological systems can lead to adverse effects on perinatal health and outcomes. Culhane asserts that the determinants of elevated risk of premature aging or “weathering” of Black Individuals can accumulate across the life course and can be contextual, behavioral, environmental, or social.20 Life course perspectives recognize that current health and health trajectories are influenced by prior physical, environmental, psychological, and social factors.21 Stressful events that occur over a life course may better explain the epidemiology and racial disparities of adverse maternal and perinatal outcomes rather than events that occur only 12 months before delivery.18 However, the risk factors that occur over a life course are difficult to quantify due to interrelation. The delay of crucial care during pregnancy and throughout the life course puts Black Individuals at a greater risk for adverse outcomes.19 As previously stated, the SDOH and external stressors experienced by Black Individuals are interrelated and can occur across a life course22; consequently, Black Individuals are disproportionately affected by structural racism, systemic racism and external stressors that can increase barriers to care and lead to adverse maternal and perinatal outcomes.23

Future interventions and recommendations to address racial disparities in adverse maternal health outcomes may benefit from taking a life course perspective – promoting health across a lifetime – especially during critical periods like pregnancy.21 The underlying causes of racial disparities are primarily rooted in systemic and structural issues, and due to the intersectionality of social determinants and intrinsic limitations of retrospective studies, causation between racial differences and maternal mortality and morbidity is difficult to establish. However, it is clear that the fragmented nature of the US healthcare system and lack of public health infrastructure has exacerbated health disparities. These disparities stem from social inequities such as lack of access to healthcare, issues in insurance coverage, implicit bias in providers, delay of care, and lack of social support. As public health studies and biomedical techniques become more sophisticated, perhaps more comprehensive interventions will be developed and lead towards the elimination of racial disparities and health inequities in the landscape of maternal-child health and beyond.

 

References

  1. The Organization for Economic Co-operation and Development (OECD). United States Department of State. Accessed December 14, 2022. https://www.state.gov/the-organization-for-economic-co-operation-and-development-oecd/
  2. Pregnancy-Related Deaths: Data from Maternal Mortality Review Committees in 36 US States, 2017–2019 | CDC. Published September 26, 2022. Accessed December 14, 2022. https://www.cdc.gov/reproductivehealth/maternal-mortality/erase-mm/data-mmrc.html
  3. MacDorman MF, Thoma M, Declcerq E, Howell EA. Racial and Ethnic Disparities in Maternal Mortality in the United States Using Enhanced Vital Records, 2016‒2017. Am J Public Health. 2021;111(9):1673-1681. doi:10.2105/AJPH.2021.306375
  4. Indicator Metadata Registry Details. Accessed December 14, 2022. https://www.who.int/data/gho/indicator-metadata-registry/imr-details/4622
  5. Fasanya HO, Hsiao CJ, Armstrong-Sylvester KR, Beal SG. A Critical Review on the Use of Race in Understanding Racial Disparities in Preeclampsia. J Appl Lab Med. 2021;6(1):247-256. doi:10.1093/jalm/jfaa149
  6. Howell EA. Reducing Disparities in Severe Maternal Morbidity and Mortality. Clin Obstet Gynecol. 2018;61(2):387-399. doi:10.1097/GRF.0000000000000349
  7. Gyamfi-Bannerman C, Srinivas SK, Wright JD, et al. Postpartum hemorrhage outcomes and race. American Journal of Obstetrics and Gynecology. 2018;219(2):185.e1-185.e10. doi:10.1016/j.ajog.2018.04.052
  8. Tucker MJ, Berg CJ, Callaghan WM, Hsia J. The Black–White Disparity in Pregnancy-Related Mortality From 5 Conditions: Differences in Prevalence and Case-Fatality Rates. Am J Public Health. 2007;97(2):247-251. doi:10.2105/AJPH.2005.072975
  9. Shahul S, Tung A, Minhaj M, et al. Racial Disparities in Comorbidities, Complications, and Maternal and Fetal Outcomes in Women with Preeclampsia/Eclampsia. Hypertens Pregnancy. 2015;34(4):506-515. doi:10.3109/10641955.2015.1090581
  10. Gad MM, Elgendy IY, Mahmoud AN, et al. Disparities in Cardiovascular Disease Outcomes Among Pregnant and Post‐Partum Women. J Am Heart Assoc. 2020;10(1):e017832. doi:10.1161/JAHA.120.017832
  11. Whitehead SJ, Berg CJ, Chang J. Pregnancy-related mortality due to cardiomyopathy: United States, 1991–1997. Obstetrics & Gynecology. 2003;102(6):1326-1331. doi:10.1016/j.obstetgynecol.2003.08.009
  12. Goland S, Modi K, Hatamizadeh P, Elkayam U. Differences in Clinical Profile of African-American Women With Peripartum Cardiomyopathy in the United States. Journal of Cardiac Failure. 2013;19(4):214-218. doi:10.1016/j.cardfail.2013.03.004
  13. Singh GK, Lee H. Trends and Racial/Ethnic, Socioeconomic, and Geographic Disparities in Maternal Mortality from Indirect Obstetric Causes in the United States, 1999-2017. Int J MCH AIDS. 2021;10(1):43-54. doi:10.21106/ijma.448
Mallory Go Nikitha Bhimireddy