The influence of detailed maternal ethnicity on cesarean delivery: findings from the U.S. birth certificate in the State of Massachusetts.

A reduction in the prevalence and variability of primary cesarean rates due to safety, quality, and cost concerns is a current focus in obstetrical care (1). Risk adjusted primary cesarean delivery rates are considered a quality performance measure and efforts to reduce these rates in low-risk primipara are a national (2) and international (3) public health priority. Yet, primary cesarean delivery rates among low-risk women in the U.S. remain high, 26.4% in 2010 (2), with wide regional and hospital variation (4; 5). Additionally, evidence of persistent racial and ethnic disparities exist, (6) which may be contributing to the variability in the overall rate of primary cesareans. Compared to Non-Hispanic white women, African American or non-Hispanic black women have higher risk adjusted rates (7). However, the data are inconsistent for Hispanic and Asian/Pacific Islander women, indicating equivalent (8), lower (9), and higher rates (10). This variation possibly reflects significant differences between subgroups of women within these broadly defined aggregates. Primary cesarean delivery rates have crucial public health significance as they are more costly to the health care system, (4) associated with increased risks for mothers and infants, (11) and contribute to the high prevalence of repeat cesareans (12). Yet, few studies (10; 13–15) have examined the racial and ethnic variability in cesarean risk among a group of women considered “low-risk” for the procedure (16)--nulliparous women with term, singleton, and vertex presentation deliveries (NTSV population). Examination of this population has four advantages. First, the definition of low risk is consistent with the Healthy People 2020 objective MICH 7.1 (2) and the Joint Commission on Accreditation in Healthcare perinatal core measure PC-02 (17), which are national and hospital-based performance measures aimed at primary cesarean reduction among the NTSV population. Second, this population is less likely to have unmeasured differences in other risk factors for cesarean delivery. The American College of Obstetrics and Gynecology recommends that inter-hospital comparisons of cesarean rates should focus on the NTSV population, as rates are expected to vary minimally under “optimal” conditions (18). Third, the influence of the management and outcome of previous pregnancies on the risk of cesarean delivery for the index pregnancy is removed. Fourth, this group is at highest risk for unplanned cesarean deliveries that may be amenable to prevention strategies (11). Racial and ethnic variation in cesarean deliveries has implications for health disparities in obstetric care. Previous studies suggest that non-white women have a disproportionately higher risk adjusted cesarean rates as compared with white women, even after taking into account socioeconomic, behavioral, medical, and institutional level factors (7–10; 13–15; 19; 20). However, with few exceptions, the applicability of these findings are limited by their use of broad racial/ethnic categories, which can mask considerable within-group heterogeneity. Therefore, this study employed a population-based dataset to examine the likelihood of primary cesarean delivery for childbearing women at low-risk for cesarean among each major ethnic group in the U.S. state of Massachusetts. We also compared our results to broad classifications of race/ethnicity more commonly employed in biomedical and public health research. The study was conducted in Massachusetts because it is one of the few U.S. states to have collected detailed ethnicity data on the birth certificate for over 15 years.