For a study, researchers sought to evaluate differences in low-risk cesarean birth rates in the United States using the Society for Maternal-Fetal Medicine (SMFM) criteria of low-risk cesarean delivery and identify characteristics associated with low-risk cesarean deliveries. They selected low-risk births for cesarean delivery using the SMFM classification based on the International Classification of Diseases, Tenth Revision, Clinical Modification codes from hospital discharge data in the 2018 National Inpatient Sample & State Inpatient Databases. Based on a nationally representative sample of hospital discharges in the National Inpatient Sample, they calculated national low-risk cesarean delivery rates overall and by patient characteristics, clinically relevant conditions not included in the SMFM criteria, and hospital characteristics. Multivariate logistic regressions were computed for the national sample to find variables related to low-risk cesarean delivery. Based on yearly state data that reflected the universe of hospital discharges from participating states in the State Inpatient Databases, they provided low-risk cesarean delivery rates for 27 states and the District of Columbia.
In the 2018 National Inpatient Sample, 2,484,874 low-risk births were included out of 3,634,724 deliveries. In 2018, the national rate of low-risk cesarean birth was 14.6% (95% CI 14.4–14.8%). However, the rates varied significantly by state (ranging from 8.9 to 18.6%). Maternal age above 40 years, non-Hispanic Black or Asian ethnicity, private insurance as the primary payer, weekday admission, obesity, diabetes, or hypertension, extensive metropolitan residency, and hospitals in the South census zone were all related to low-risk cesarean delivery. Using the SMFM criterion, 1 in every 7 low-risk births in the United States in 2018 was via cesarean, and the low-risk cesarean delivery rates varied greatly by state.