What’s behind the wide variation in US cesarean rates?

A study of nearly 1.5 million births in the United States shows that while rates of cesarean delivery vary widely from hospital to hospital, identifying the underlying cause with existing data is difficult. The findings underscore a need for collection by hospitals of comprehensive patient data in order to fully understand and optimize use of cesarean delivery.

Reporting in PLOS Medicine, researchers from the University of Minnesota School of Public Health and Harvard University analyzed data from the 2009 and 2010 Nationwide Inpatient Sample from the Healthcare Cost and Utilization Project, a 20% sample of hospitals in the United States. Their findings are based on 1,475,457 births at 1373 hospitals.

Covariates used included hospital size, location, and whether an institution was a teaching institution; the mother’s age, insurance status, and race/ethnicity; and fetal distress, fetal disproportion or obstructed labor, hemorrhage during pregnancy, placental complications, hypertension during the pregnancy, and a diagnosis of diabetes in pregnancy.

Among all births, the average hospital prevalence of cesarean delivery was 33.0% (95% confidence interval [CI] 32.9% to 33.1%). The mean prevalence of primary cesarean delivery, was 22.0% (95% CI 22.0% to 22.1%). Primary cesarean deliveries were more prevalent in women with diabetes (34.5%), hypertension in pregnancy (41.4%), hemorrhage during pregnancy or placental complications (57.9%), fetal distress (58.2%), fetopelvic disproportion or obstruction of labor (58.4%), or maternal age ≥35 (28.0%).

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Across hospitals, the risk of having a cesarean delivery was 19% to 48% and did not decrease after adjustment for individual diagnoses and sociodemographic and hospital factors. In women at higher risk (preterm, multiple gestation, or nonvertex pregnancy or prior cesarean), the likelihood of cesarean varied from 56% to 92% across institutions. Prevalence of cesarean was higher among black women and those whose delivered in either urban hospitals or hospitals with larger volumes.

The study was limited in that nulliparous women in the cohort were not identified and no information was included on gestational age. In addition, no clinical details about the reasons for cesarean delivery were reported in the discharge data, preventing the researchers from assessing the appropriateness of care or if clinical reasons could explain the variations.

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