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Contents: Original Research

Racial and Ethnic Disparities in Maternal Morbidity and Obstetric Care

Grobman, William A. MD, MBA; Bailit, Jennifer L. MD, MPH; Rice, Madeline Murguia PhD; Wapner, Ronald J. MD; Reddy, Uma M. MD, MPH; Varner, Michael W. MD; Thorp, John M. Jr MD; Leveno, Kenneth J. MD; Caritis, Steve N. MD; Iams, Jay D. MD; Tita, Alan T.N. MD, PhD; Saade, George MD; Rouse, Dwight J. MD; Blackwell, Sean C. MD; Tolosa, Jorge E. MD, MSCE; VanDorsten, J. Peter MD for the Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD) Maternal-Fetal Medicine Units (MFMU) Network

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doi: 10.1097/AOG.0000000000000735

Racial and ethnic disparities in health care have been defined as differences in the quality of care received by particular groups who have similar health insurance and the same access to a doctor when there are no differences between these groups in their preferences and needs for treatment.1 In their report on health disparities, the Institute of Medicine indicated that racial and ethnic minorities in the United States are less likely to receive needed procedures, more likely to receive less useful procedures, and overall experience a lower quality of health services.1 For example, black men and women in the United States have been shown to have higher mortality related to coronary heart disease but lower rates of receiving coronary angioplasty and bypass surgery than their white counterparts.2

Health disparities also have been documented in reproductive health.3 Many studies have demonstrated the marked black–white difference that exists in both infant and maternal mortality.4–6 These differences do not appear to be related solely to a greater prevalence or severity of obstetric complications. Both Tucker et al7 and Rosenberg et al,8 for example, have shown that black women are more likely to have pregnancy-associated mortality even after accounting for severity of who reached complete dilation.

It has been less well documented whether disparities exist with regard to significant maternal morbidities. Some studies have suggested that white women are less likely to experience postpartum hemorrhage, infection, and severe perineal laceration than other racial and ethnic groups.9–12 However, these studies typically have used administrative databases and therefore have not been able to adjust adequately for potential differences in other patient characteristics (eg, age, body mass index [BMI]) that might account for the disparities. Also, these studies as well as the ones that have evaluated maternal mortality have not been able to assess whether there are corresponding differences in the obstetric care that was received by women of different racial and ethnic status.

In this study, we have used data from an observational obstetric cohort designed to evaluate the quality of obstetric care in an effort to determine whether there are racial and ethnic differences in the frequency of three significant maternal morbidities (severe postpartum hemorrhage, peripartum infection, and severe perineal laceration) as well as differences in related obstetric care.


Between 2008 and 2011, investigators at 25 medical centers of the Eunice Kennedy Shriver National Institute of Child Health and Human Development Maternal-Fetal Medicine Units Network assembled an observational obstetric cohort (ie, the Assessment of Perinatal EXcellence study) that included detailed information collected by trained and certified nurses on patient characteristics, intrapartum events, and pregnancy outcomes. Institutional review board approval for the study and a waiver of informed consent were obtained at all centers. Full details of the technique of data collection have been described previously.13,14

Racial and ethnic status, as documented in patients' charts, was recorded in the database. The present analysis excludes those women who had no race or ethnicity recorded or whose race and ethnicity was categorized as “other.” All other women in the registry were included in the analysis and had race and ethnicity categorized as non-Hispanic white, non-Hispanic black, Hispanic, or Asian. Characteristics of the population by race and ethnicity were assessed in univariable analysis using the χ2 test.

The frequency of severe postpartum hemorrhage (defined as estimated blood loss 1,500 cc or greater at delivery or the immediate postpartum period, a blood transfusion, or a hysterectomy for hemorrhage, placenta accreta, or atony), peripartum infection (defined as chorioamnionitis, endometritis, wound cellulitis requiring antibiotics, wound reopened for fluid collection or infection, or wound dehiscence during the delivery hospitalization), and severe perineal laceration at spontaneous vaginal delivery (defined as a third- or fourth-degree laceration) was compared among the racial and ethnic groups. These outcomes were chosen given that they were the primary maternal morbidity outcomes in the Assessment of Perinatal EXcellence study, are acknowledged to be important health outcomes, and, because they may be modified by care within the health care system, have a conceptually plausible relationship with regard to racial disparities. To determine whether any noted racial and ethnic differences could be related to differences in demographic and historical characteristics other than race and ethnicity, we used multivariable logistic regression with non-Hispanic white women as the referent to adjust for patient characteristics and to estimate whether the association between race and ethnicity and each outcome, presented as odds ratios with 95% confidence intervals (CIs), persisted. The multivariable models including patient factors were based on risk-adjusted models previously developed, using derivation and validation data sets, for the three maternal adverse outcomes.13 Another possible explanation for differences in morbidity could be that women of different race and ethnicity disproportionately receive care at certain institutions with different patterns of care or different frequencies of health outcomes.15,16 To evaluate this possibility, the hospital of delivery was added to the multivariable logistic regression models. In addition, the interaction between hospital of delivery and race and ethnicity was evaluated. Odds ratios (ORs) and 95% CIs for the association between race and ethnicity again were reestimated.

Lastly, the association between types of obstetric care provided (eg, episiotomy) and race and ethnicity was explored. Previous analyses in this cohort have demonstrated that, even after adjusting for patient, health care provider, and institutional factors, several types of obstetric care are associated with postpartum hemorrhage, peripartum infection, and severe perineal laceration.14 The frequencies of these types of obstetric care were compared among the different racial and ethnic groups. Multivariable logistic regression was used to estimate the OR and 95% CI for the association between race and ethnicity and types of obstetric care after controlling for differences in patient characteristics and hospital of delivery.

All tests were two-tailed; P<.05 was used to define statistical significance for descriptive analyses and P<.001 was used to account for multiple hypothesis testing of adverse maternal outcomes and types of obstetric care. No imputation for missing data was performed. All analyses were performed with SAS.


During the study, 115,502 women delivered and their data were collected for the Assessment of Perinatal EXcellence study. Of these, 109,208 (95%) were classified according to one of the defined race and ethnicity categories and included in the present analysis. The study population was 48% (n=52,040) non-Hispanic white, 22% (n=23,878) non-Hispanic black, 25% (n=27,291) Hispanic, and 5% (n=5,999) Asian. There were multiple differences among women of different race and ethnicity with regard to their patient characteristics and medical history (Table 1).

Table 1-a
Table 1-a:
Patient Characteristics by Race and Ethnicity
Table 1-b
Table 1-b:
Patient Characteristics by Race and Ethnicity

The frequency of adverse maternal outcomes, stratified by race and ethnicity, is presented in Table 2. For each outcome, disparities by race and ethnicity existed with non-Hispanic white women being least likely to experience severe postpartum hemorrhage or peripartum infection and Asian women most likely to experience a severe perineal laceration at spontaneous vaginal delivery (P<.001 for all).

Table 2
Table 2:
Associations Between Race and Ethnicity and Adverse Maternal Outcomes

These racial and ethnic differences largely persisted after controlling for other differences in patient characteristics and hospital of delivery (Table 2). Non-Hispanic black, Hispanic, and Asian women all had significantly greater odds of experiencing a severe postpartum hemorrhage or peripartum infection than non-Hispanic white women. Moreover, as the adjusted ORs demonstrate, the magnitude of the differences for severe postpartum hemorrhage and peripartum infection did not notably change from their unadjusted estimate even after patient characteristics and delivery hospital were included in the regression.

Disparities in the frequency of severe perineal laceration similarly persisted after adjustment, although the pattern of difference among the groups, like in the univariable analysis, was different than that observed for severe postpartum hemorrhage and peripartum infection. Compared with non-Hispanic white women, Asian women had significantly higher odds of laceration, whereas non-Hispanic black women had significantly lower odds of laceration. Of note, differences in patient characteristics appeared to explain some, but not all, of the disparity, because the difference between non-Hispanic white and Hispanic women was no longer present, and the magnitude of the difference between non-Hispanic white and non-Hispanic black women was attenuated and no longer significant at the P<.001 level after adjustment for patient characteristics. Interaction terms between each delivery hospital and race and ethnicity were examined and all were nonsignificant.

Racial and ethnic differences existed not only for adverse maternal outcomes, but for types of obstetric care previously shown14 to be associated with these outcomes (Table 3). The frequency of every type of care that was assessed varied, sometimes widely, among the different race and ethnicity groups. For example, Asian women were most likely to receive an episiotomy. Also, non-Hispanic white women were more likely to undergo labor induction compared with all the other race and ethnicity groups. The associations between race and ethnicity and types of care received generally persisted despite adjustment for patient characteristics or delivery hospital.

Table 3
Table 3:
Associations Between Race and Ethnicity and Types of Obstetric Care


In this analysis, we have demonstrated that racial and ethnic differences exist in the frequency of significant maternal morbidities. Specifically, severe postpartum hemorrhage and peripartum infection are least common among non-Hispanic white women, whereas severe perineal lacerations are most common among Asian women. These differences do not appear to be explained by differences in other patient characteristics such as parity, age, BMI, or socioeconomic indicators such as insurance status. The differences also do not appear to be related to the possibility that women of a particular race and ethnicity are more likely to be admitted to hospitals with higher rates of these adverse outcomes. Indeed, as the nonsignificance of the interaction terms between race and ethnicity and hospitals demonstrate, the racial and ethnic differences are similar among all hospitals studied.

There has been a large body of work that has demonstrated racial and ethnic differences in obstetric mortality.3,7,8 There has been much less research into differences in maternal morbidities. The studies that do exist have demonstrated racial and ethnic differences in outcomes that are similar to the ones noted in the present analysis. Because prior studies largely have been derived from administrative databases, which have not allowed detailed patient risk adjustment or adjustment for the admitting hospital, the potential for confounding for the racial and ethnic differences has remained.9–12 The present analysis, which has used data collected by direct chart abstraction by trained research personnel, suggests that the racial and ethnic differences in maternal morbidities that were observed cannot easily be explained by differences in other patient characteristics or the hospital in which care was provided.

This study also has shown that it is not just outcomes that differ among women of different race and ethnicity, but the frequencies of certain types of obstetric care as well. As one example, the frequency of receiving an episiotomy was significantly higher for Asian women. The reasons for this increased utilization are not clear, because other patient characteristics, such as BMI and parity, did not account for this difference. It is notable, however, that use of episiotomy has been associated with a greater chance of severe perineal lacerations,14,17,18 which, in the present study, were most likely to be experienced by Asian women as well. The racial and ethnic differences in outcomes, the inability to explain these differences based on case mix, and the observed differences in care processes that have been related to those outcomes suggest that differences in care may be one explanation for the racial and ethnic differences in outcomes that were observed.

Nevertheless, the reason that there are racial and ethnic differences in obstetric care is uncertain. Unlike cardiac catheterization, for which there are well-established guidelines with regard to the appropriateness of the procedure,1,2,16 many obstetric interventions (eg, episiotomy, vaginal examinations, delayed pushing) do not have guidelines that are as clear. Accordingly, whether these procedures were truly underused or overused for a given group cannot be known. It is possible that our risk adjustment models did not include all observable patient characteristics that could confound the association between race and ethnicity and the outcome, yet these models were developed using derivation and validation data sets, considered a wide variety of factors plausibly related to the outcomes, and produced area under the curves of the receiver operating characteristic curves that are similar to other accepted risk adjustment models.13 Also, it is possible that there are differences in patient preferences or in unmeasured and nonmodifiable patient factors that could explain the observed associations. Finally, it was not specified in patients' charts how race and ethnicity was assigned and it remains unknown, for example, whether all assignments were based on self-identification. It is unknown whether further information about the method by which race and ethnicity was assigned would alter our findings.

Correspondingly, determining the origin of the racial and ethnic differences in maternal care and morbidity should be a priority. Maternal mortality has been rising in the United States and a persistent racial and ethnic gap remains.3,19 Obstetric morbidity, however, is much more frequent than obstetric mortality and can serve as a more readily accessible measure to identify quality improvement targets.20 Similarly, unexplained variation in health care processes (such as the frequency of admission in early labor or the delay in pushing in the second stage) may serve to highlight areas where determination of best practices and corresponding guidelines would be helpful. Such an approach may not only result in reductions in maternal morbidity but, ultimately, in maternal mortality as well.


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