In 2012, the Society for Maternal-Fetal Medicine, the Eunice Kennedy Shriver National Institute of Child Health and Human Development, and the American College of Obstetricians and Gynecologists convened to review evidence for labor management strategies designed to safely reduce the rate of cesarean delivery.1 This was followed by publication of an Obstetric Care Consensus on prevention of primary cesarean delivery, which included guidelines regarding labor management best practices.2
Although the evidence for labor management best practices should be applied similarly to women of different races and ethnicities, disparities in obstetric care exist.3–6 Health disparities, or systematic differences in health status that “negatively impact less advantaged groups,”7 exist in many aspects of maternal and neonatal morbidity and mortality.3–6 For example, non-Hispanic black women experience greater cesarean delivery frequency than non-Hispanic white women, even after adjusting for risk factors.3,8–12 Health care disparities are differences in quality of care received by individuals in particular groups even when factors such as preferences and access are similar.13 Several racial and ethnic disparities in obstetric care have been identified, including for labor induction, delayed pushing, and analgesia use.3,14,15 However, it is unknown whether care disparities explain the racial and ethnic disparity in cesarean delivery frequency.3,16
Achieving health equity requires understanding determinants of disparities.17,18 Because reasons for the cesarean delivery disparity among minority women remain poorly characterized, we evaluated whether evidence regarding the safe promotion of vaginal delivery was applied differently based on maternal race and ethnicity. Our objectives were to examine whether racial and ethnic differences exist in the frequency of and indications for cesarean delivery and to determine whether these differences may be explained by disparities in the application of labor management strategies intended to reduce the frequency of cesarean deliveries.2
MATERIALS AND METHODS
This is a secondary analysis of the Assessment of Perinatal Excellence study, a large, multicenter observational study performed at 25 hospitals in the United States. Assessment of Perinatal Excellence methodology has been previously reported.19,20 The Assessment of Perinatal Excellence cohort consisted of 115,502 women and their neonates who delivered at participating hospitals from 2008 to 2011. Study patients represented a diverse sample of sociodemographic characteristics and were sampled according to plans designed to avoid overrepresentation of patients from larger hospitals. Accoucheurs included general obstetricians, family medicine physicians, midwives, and maternal–fetal medicine physicians.19,20 Clinical data for patients who were at least 23 weeks of gestation and who had arrived at the hospital with a live fetus were collected by trained research personnel at each site. Maternal characteristics, details of the medical and obstetric history, intrapartum care, obstetric outcome, and indications for operative procedures were collected. Maternal race and ethnicity as reported in the chart were abstracted from the medical record. Institutional review board approval was obtained from all participating centers under a waiver of informed consent.
For this analysis, we analyzed two cohorts comprised of term, singleton, nonanomalous, vertex, liveborn neonates. The first cohort consisted of nulliparous women. The second cohort was composed of multiparous women with prior vaginal deliveries only. In both cohorts, women who were ineligible for vaginal deliveries (placenta previa, placenta accreta, prior cavity-entering myomectomy or classical cesarean delivery, active herpes infection) were excluded.
We first evaluated the frequencies of, and indications for, cesarean delivery. The indications assessed included nonreassuring fetal status, labor dystocia (inclusive of arrest of dilation, arrest of descent, or failed induction of labor), suspected macrosomia, elective, and “other” reasons (such as abruption or maternal medical complications).
In the nulliparous cohort, utilization of strategies intended to promote vaginal delivery was then evaluated using the American College of Obstetricians and Gynecologists and Society for Maternal-Fetal Medicine Consensus2 as a framework to guide the labor management strategies analyzed. Although the Consensus2 was published after the Assessment of Perinatal Excellence data accrual period, the evidence for these guidelines was accumulated before and during the Assessment of Perinatal Excellence period. First, for failed induction of labor, we assessed the proportion of women who underwent cesarean delivery performed for a diagnosis of failed induction before 5 cm cervical dilation and before 12 hours of oxytocin and rupture of membranes (whichever came last).2,21–23 We additionally assessed the proportion of women with an unfavorable cervical examination (modified Bishop score less than 5) who underwent labor induction without cervical ripening compared with those undergoing induction with cervical ripening.2,24,25 For arrest of dilation, we assessed the proportion of women whose cesarean delivery for an indication of arrest of labor was performed before 4 hours of labor dystocia after reaching 5 cm cervical dilation with ruptured membranes.2,26–28 Determination of labor dystocia with regard to uterine activity was made by individual providers; Assessment of Perinatal Excellence does not have information about uterine activity. For both failed induction and arrest of dilation, 5 cm was chosen for this analysis because of availability of this landmark in the Assessment of Perinatal Excellence database and prior use of 5 cm in the diagnosis of failed labor induction.22 For arrest of descent, we assessed the proportion of women undergoing cesarean delivery for an indication of arrest of descent before 3 hours in the second stage.2,29–31 Finally, given that there is no standard to know whether the diagnosis of nonreassuring fetal status was differentially applied, we examined the proportion of women who underwent cesarean delivery for an indication of nonreassuring fetal status with a 1-minute Apgar score of 7 or greater. As a result of smaller sample sizes, we were not able to evaluate utilization of all of these labor management strategies in the multiparous cohort.
The outcomes that incorporate time were also evaluated as continuous variables: duration of induction before diagnosis of a failed induction (as defined previously); duration of active labor before a diagnosis of arrest of dilation (length of time from 5 cm until decision for cesarean delivery); and the duration of second stage before diagnosis of arrest of descent (length of time from complete dilation until decision for cesarean delivery).
The Kruskal-Wallis test for continuous variables and the χ2 test for categorical variables were used to describe baseline demographic and clinical characteristics by maternal race and ethnicity. Multivariable logistic regression was used to evaluate binomial outcomes (cesarean delivery, adherence to failed induction guideline, adherence to cervical ripening guideline, adherence to arrest of dilation guideline, adherence to arrest of descent guideline, cesarean performed for nonreassuring fetus status with 1-minute Apgar 7 or greater, and the composite). Multivariable multinomial logistic regression was used to evaluate the indication for cesarean delivery, an outcome with more than two categories. The continuous outcomes were evaluated using comparisons of least squares means based on multivariable linear regression. All models were adjusted for age, body mass index, gestational age at delivery, diabetes, smoking, chorioamnionitis, and gestational hypertension or preeclampsia. As a result of equipoise regarding whether payer status was in the causal pathway between maternal race and cesarean delivery rates, a secondary analysis was performed with insurance status included in the regression. Hospital was also included in the models as a fixed effect. Imputation for missing data was not performed. SAS was used for the analyses. All tests were two-tailed and a P value of <.05 was used to define statistical significance.
A total of 75,400 women were eligible for inclusion, of whom 47% (n=35,529) were in the nulliparous cohort and 53% (n=39,871) were in the multiparous cohort. The majority of hospitals were teaching hospitals (22/25 [88%]). Of the 35,529 women eligible for analysis in the nulliparous cohort, 25.8% (9,156) underwent cesarean delivery (Table 1). There were a number of differences in demographic and clinical characteristics between racial and ethnic groups. Non-Hispanic black and Hispanic women were more likely to have government-assisted insurance and non-Hispanic white women were more likely to smoke. Asian women were more likely to have gestational diabetes mellitus, whereas non-Hispanic black women were more likely to have pregestational diabetes mellitus, chronic hypertension, or gestational hypertension or preeclampsia.
In the nulliparous cohort, the cesarean delivery frequencies were 25.0%, 28.3%, 28.7%, and 24.0% for non-Hispanic white, non-Hispanic black, Asian, and Hispanic women, respectively (Table 2). When adjusting for patient characteristics and hospital, the odds of cesarean delivery were higher in all racial and ethnic minority groups compared with non-Hispanic white women. This finding was related to both a greater odds of cesarean delivery for nonreassuring fetus status and labor dystocia (inclusive of arrest of dilation, arrest of descent, and failed induction) in all racial and ethnic groups compared with non-Hispanic white women. Notably, non-Hispanic black women had a twofold increase in odds of cesarean delivery for nonreassuring fetus status (adjusted odds ratio [OR] 2.39, 95% CI 2.13–2.69) compared with non-Hispanic white women. Conversely, non-Hispanic black (adjusted OR 0.49, 95% CI 0.34–0.72) and Asian (adjusted OR 0.48, 95% CI 0.28–0.81) women experienced lower odds of cesarean delivery for suspected macrosomia, and Hispanic women experienced lower odds of elective cesarean delivery (adjusted OR 0.60, 95% CI 0.42–0.87), compared with non-Hispanic white women.
Among the 39,871 multiparous women with prior vaginal deliveries only, the overall frequency of cesarean delivery was 6.0%. The frequencies of cesarean delivery were 4.9%, 8.4%, 5.8%, and 6.0%, for non-Hispanic white, non-Hispanic black, Asian, and Hispanic women, respectively (Table 3). Non-Hispanic black women experienced greater odds of cesarean delivery overall (adjusted OR 1.51, 95% CI 1.33–1.70), mainly attributed to increased odds of cesarean delivery for nonreassuring fetus status and labor dystocia compared with non-Hispanic white women. Hispanic women had greater odds of having cesarean delivery for nonreassuring fetus status and labor dystocia compared with non-Hispanic white women. In contrast, non-Hispanic black and Asian women experienced lower odds of cesarean delivery for suspected macrosomia, and non-Hispanic black and Hispanic women experienced lower odds of elective cesarean delivery.
Nevertheless, women with racial and ethnic minority status did not experience higher frequencies of cesarean delivery secondary to differential application of labor management strategies or adherence to professional societies' guidelines for preventing cesarean delivery (Table 4). Specifically, more than three fourths of women who underwent cesarean delivery for failed induction had that cesarean delivery performed before 12 hours of oxytocin and ruptured membranes, approximately 20% of women undergoing labor induction with an unfavorable cervix did not receive cervical ripening, and more than half of women who underwent cesarean delivery for arrest of descent were delivered before 3 hours in the second stage, yet the odds of these occurrences were similar across all racial and ethnic groups. Also, approximately one fourth of all women who underwent cesarean delivery for arrest of dilation were delivered before 4 hours of labor dystocia, although Hispanic women actually had decreased odds compared with non-Hispanic white women (adjusted OR 0.67, 95% CI 0.49–0.92). Finally, in all racial and ethnic groups, more than three fourths of women experiencing cesarean delivery for nonreassuring fetus status had neonates with 1-minute Apgar scores 7 or greater; however, Asian women were at increased odds of this scenario (adjusted OR 1.79, 95% CI 1.07–3.00). The composite outcome (comprised of each of the previously mentioned scenarios) did not differ by race and ethnicity.
The evaluation of continuous outcomes also could not explain the racial and ethnic differences in cesarean delivery frequencies among the specific denominators. There were no differences in adjusted mean hours from oxytocin or rupture of membranes (whichever came last) to cesarean delivery decision for failed induction by maternal race and ethnicity. Non-Hispanic black, Hispanic, and Asian women who reached 5 cm cervical dilation remained pregnant for a greater number of hours after 5 cm dilation and before a decision was made to proceed with cesarean delivery for arrest of dilation compared with non-Hispanic white women (Table 5). In contrast, Asian women had a lower adjusted mean number of hours in the second stage before the cesarean delivery decision, although this finding does not fully explain the higher rate of cesarean delivery among Asian women given the nonsignificant association between cesarean delivery for arrest of descent before 3 hours of the second stage and Asian race in categorical analyses.
Finally, all models were performed with inclusion of insurance status in the regression. Inclusion of insurance status in the regression equations did not materially alter any results (data not shown). Specifically, inclusion of insurance status in the model did not alter the significance of any findings for nulliparous women, including indications for cesarean delivery, the application of labor management strategies for preventing cesarean delivery, or the duration of time until cesarean delivery. However, for multiparous women with prior vaginal deliveries, the inclusion of insurance status in the model resulted in no association between Hispanic ethnicity and cesarean delivery for nonreassuring fetus status (adjusted OR 1.21, 95% CI 0.94–1.55) or elective cesarean delivery (adjusted OR 0.73, 95% CI 0.48–1.12); no other differences were identified for women in other racial and ethnic groups.
Our data showed that non-Hispanic black, Asian, and Hispanic women all experience greater likelihood of cesarean delivery than non-Hispanic white women, even after accounting for sociodemographic and clinical differences, and that indications for cesarean delivery vary by maternal race and ethnicity. However, we did not identify differences in care provision by maternal race and ethnicity. Notably, among nulliparous women, the differential odds of cesarean delivery could not be traced to differential application of guidelines for failed induction of labor, arrest of dilation, arrest of descent, nonreassuring fetus status, or cervical ripening.
Understanding sources of disparities is essential to promoting equity in health care delivery. We designed this investigation to determine whether women of racial and ethnic minority status were more likely to experience cesarean delivery as a result of differences in application of labor management strategies intended to promote safe vaginal delivery.1,2 Disparities in application of professional guidelines have been well documented in other areas of medicine.13 Our findings regarding disparities in cesarean delivery indication have been seen in other cohorts. For example, Edmonds et al9 demonstrated non-Hispanic black women experienced greater odds of cesarean delivery for fetal distress or failure to progress, and others have identified non-Hispanic black women were more likely to experience cesarean delivery for nonreassuring fetus status,10,12 yet the reasons for these disparities in overall rate and indication remain unknown.10,11,32 Although some have hypothesized minority women are at greater risk of cesarean delivery for “subjective” indications such as nonreassuring fetus status,10 our data do not support this hypothesis. This finding is consistent with data from a 1997–2002 California cohort in which, although specific labor and delivery practices could not be examined, racial differences in the cesarean delivery rate were not fully explained by delivery hospital or physician.33
Identifying the roots of disparities in obstetric outcomes requires understanding differences in care provision. These findings suggest that labor management strategies to promote vaginal delivery are not differentially applied by maternal race and ethnicity. It is unclear that differences in frequency of nonreassuring fetus status or labor dystocia are the result of true biological differences; however, it is plausible that other mediating factors may underlie these disparities. For example, the greater frequencies of hypertensive disorders and small-for-gestational-age neonates16,34 among minority women may contribute to the greater likelihood of cesarean delivery for nonreassuring fetus status. Others have hypothesized that differential outcomes of labor induction may be the result of differential pharmacologic response to induction agents.35,36 Perhaps these findings warrant investigation into individualized responses to induction or augmentation agents, particularly in this era of precision medicine.37 However, any of these possibilities are speculative, and next steps must include multidisciplinary investigation of other patient- and health care provider-centered reasons for the identified disparities.
Strengths of this analysis include the large cohort with detailed information about patient characteristics and features of labor and delivery. In addition to having indications for cesarean delivery, we were able to take advantage of the granularity of APEX data to investigate specific labor and delivery management. Moreover, data were collected by trained research personnel at clinically and geographically diverse settings. However, several limitations warrant note. Evidence from the Consortium on Safe Labor has suggested using 6 cm as a cutoff for active labor,38 but the Assessment of Perinatal Excellence study collected information on time of achieving 5 cm cervical dilation. Additionally, as is necessary for the nature of this question, these data are observational and cannot demonstrate causation. We are also unable to account for the role of health care provider type, because Assessment of Perinatal Excellence collected the delivering attending as the assigned health care provider, which may not have been the same health care provider type as the individual managing the patient's labor. Furthermore, the majority of hospitals were teaching hospitals, which limits the generalizability of the findings. Finally, as a result of small numbers for some racial and ethnic groups, we were not able to evaluate specific types of care in the cohort of multiparous women with prior vaginal deliveries only.
Understanding whether and how maternal race and ethnicity influence the complex decision-making processes that take place in obstetric care is critical to improving the quality of care for all women. Although women of minority racial and ethnic status experience greater likelihood of cesarean delivery as well as differences in indications for cesarean delivery, our data suggest these differences are not clearly attributed to unequal application of labor management strategies intended to promote safe vaginal deliveries. Although these findings may offer some reassurance about equity in care provision, the racial and ethnic disparities in cesarean delivery and other maternal and neonatal health outcomes remain and the reasons for these differences continue to require elucidation.
1. Spong CY, Berghella V, Wenstrom KD, Mercer BM, Saade GR. Preventing the first cesarean delivery: summary of a joint Eunice Kennedy Shriver National Institute of Child Health and Human Development, Society for Maternal-Fetal Medicine, and American College of Obstetricians and Gynecologists Workshop. Obstet Gynecol 2012;120:1181–93.
2. Safe prevention of the primary cesarean delivery. Obstetric Care Consensus No. 1. American College of Obstetricians and Gynecologists. Obstet Gynecol 2014;123:693–711.
3. Grobman WA, Bailit JL, Rice MM, Wapner RJ, Reddy UM, Varner MW, et al. Racial and ethnic disparities in maternal morbidity and obstetric care. Obstet Gynecol 2015;125:1460–7.
4. Creanga AA, Bateman BT, Kuklina EV, Callaghan WM. Racial and ethnic disparities in severe maternal morbidity: a multistate analysis, 2008-2010. Am J Obstet Gynecol 2014;210:435.e1–8.
5. Creanga AA, Berg CJ, Syverson C, Seed K, Bruce FC, Callaghan WM. Pregnancy-related mortality in the United States, 2006-2010. Obstet Gynecol 2015;125:5–12.
7. Dehlendorf C, Bryant AS, Huddleston HG, Jacoby VL, Fujimoto VY. Health disparities: definitions and measurements. Am J Obstet Gynecol 2010;202:212–3.
8. Min CJ, Ehrenthal DB, Strobino DM. Investigating racial differences in risk factors for primary cesarean delivery. Am J Obstet Gynecol 2015;212:814.e1–4.
9. Edmonds JK, Yehezkel R, Liao X, Moore Simas TA. Racial and ethnic differences in primary, unscheduled cesarean deliveries among low-risk primiparous women at an academic medical center: a retrospective cohort study. BMC Pregnancy Childbirth 2013;13:168.
10. Washington S, Caughey AB, Cheng YW, Bryant AS. Racial and ethnic differences in indication for primary cesarean delivery at term: experience at one U.S. institution. Birth 2012;39:128–34.
11. Bryant AS, Washington S, Kuppermann M, Cheng YM, Caughey AB. Quality and equality in obstetric care: racial and ethnic differences in caesarean section delivery rate. Paediatr Perinatal Epidemiol 2009;23:454–62.
12. Getahun D, Strickland D, Lawrence JM, Fassett MJ, Koebnick C, Jacobsen SJ. Racial and ethnic disparities in the trends in primary cesarean delivery based on indications. Am J Obstet Gynecol 2009;201:422.e1–7.
13. Institute of Medicine. Unequal treatment: confronting racial and ethnic disparities in health care. Washington, DC: The National Academies Press; 2003.
14. Butwick AJ, Blumenfeld YJ, Brookfield KF, Nelson LM, Weiniger CF. Racial and ethnic disparities in mode of anesthesia for cesarean delivery. Anesth Analg 2016;122:472–9.
15. Toledo P, Sun J, Grobman WA, Wong CA, Feinglass J, Hasnain-Wynia R. Racial and ethnic disparities in neuraxial labor analgesia. Anesth Analg 2012;114:172–8.
16. Hamilton BE, Martin JA, Osterman MJ, Curtin SC, Mathews T. Births: final data for 2014. Natl Vital Stat Rep 2015;64:1–64.
17. Eichelberger KY, Doll K, Ekpo GE, Zerden ML. Black lives matter: claiming a space for evidence-based outrage in obstetrics and gynecology. Am J Public Health 2016;106:1771–2.
18. Institute of Medicine. How far have we come in reducing health disparities? Progress since 2000: workshop summary. Washington, DC: The National Academies Press; 2012.
19. Grobman WA, Bailit JL, Rice MM, Wapner RJ, Varner MW, Thorp JM Jr, et al. Can differences in obstetric outcomes be explained by differences in the care provided? The MFMU network APEX study. Am J Obstet Gynecol 2014;211:147e1–16.
20. Bailit JL, Grobman WA, Rice MM, Spong CY, Wapner RJ, Varner MW, et al. Risk-adjusted models for adverse obstetric outcomes and variation in risk-adjusted outcomes across hospitals. Am J Obstet Gynecol 2013;209:446.e1–30.
21. Simon CE, Grobman WA. When has an induction failed? Obstet Gynecol 2005;105:705–9.
22. Rouse DJ, Weiner SJ, Bloom SL, Varner MW, Spong CY, Ramin SM, et al. Failed labor induction: toward an objective diagnosis. Obstet Gynecol 2011;117:267–72.
23. Rouse DJ, Owen J, Hauth JC. Criteria for failed labor induction: prospective evaluation of a standardized protocol. Obstet Gynecol 2000;96:671–7.
24. Jozwiak M, Bloemenkamp KW, Kelly AJ, Mol BW, Irion O, Boulvain M. Mechanical methods for induction of labor. The Cochrane Database of Systematic Reviews 2012, Issue 3. Art. No.: CD001233.
25. Hofmeyr GJ, Gülmezoglu AM, Pileggi C. Vaginal misoprostol for cervical ripening and induction of labor. The Cochrane Database of Systematic Reviews 2010, Issue 10. Art. No.: CD000941.
26. Rouse DJ, Owen J, Hauth JC. Active-phase labor arrest: oxytocin augmentation for at least 4 hours. Obstet Gynecol 1999;93:323–8.
27. Rouse DJ, Owen J, Savage KG, Hauth JC. Active phase labor arrest: revisiting the 2-hour minimum. Obstet Gynecol 2001;98:550–4.
28. Henry DE, Cheng YW, Shaffer BL, Kaimal AJ, Bianco K, Caughey AB. Perinatal outcomes in the setting of active phase arrest of labor. Obstet Gynecol 2008;112:1109–15.
29. Rouse DJ, Weiner SJ, Bloom SL, Varner MW, Spong CY, Ramin SM, et al. Second-stage labor duration in nulliparous women: relationship to maternal and perinatal outcomes. Am J Obstet Gynecol 2009;201:357.e1–7.
30. Le Ray C, Audibert F, Goffinet F, Fraser W. When to stop pushing: effects of duration of second-stage expulsive efforts on maternal and neonatal outcomes in nulliparous women with epidural analgesia. Am J Obstet Gynecol 2009;201:361.e1–7.
31. Cheng YW, Hopkins LM, Caughey AB. How long is too long: does a prolonged second stage of labor in nulliparous women affect maternal and neonatal outcomes? Am J Obstet Gynecol 2004;191:933–8.
32. Kabir AA, Pridjian G, Steinmann WC, Herrera EA, Khan MM. Racial differences in cesareans: an analysis of U.S. 2001 National Inpatient Sample Data. Obstet Gynecol 2005;105:710–8.
33. Chung JH, Garite TJ, Kirk AM, Hollard AL, Wing DA, Lagrew DC. Intrinsic racial differences in the risk of cesarean delivery are not explained by differences in caregivers or hospital site of delivery. Am J Obstet Gynecol 2006;194:1323–8.
34. Martin JA, Hamilton BE, Ventura SJ, Osterman MJ, Kirmeyer S, Mathews TJ, et al. Births: final data for 2009. Natl Vital Stat Rep 2011;60:1–70.
35. Stephenson ML, Hawkins JS, Pevzner L, Powers BL, Wing DA. Racial/ethnic differences in labor outcomes with prostaglandin vaginal inserts. J Racial Ethn Health Disparities 2015;2:149–57.
36. Wing DA, Sheibani L. Pharmacotherapy options for labor induction. Expert Opin Pharmacother 2015;16:1657–68.
37. Precision Medicine Initiative Working Group Report to the Advisory Committee to the Director of the National Institutes of Health. The precision medicine initiative cohort program—building a research foundation for 21st century medicine. Washington, DC: National Institutes of Health; 2015.
38. Zhang J, Landy HJ, Branch DW, Burkman R, Haberman S, Gregory KD, et al. Contemporary patterns of spontaneous labor with normal neonatal outcomes. Obstet Gynecol 2010;116:1281–7.