A new study set out to explore the hypothesis that higher volume hospitals have fewer cesarean deliveries and lower morbidity among women delivering twins. The results were published in the American Journal of Perinatology, 2017. Data for the study was obtained from the 2011 Nationwide Inpatient Sample (NIS). The researchers stated that the NIS is the largest publically available all-payer inpatient database. NIS samples 20 percent of hospitals in the United States annually. The database consists of approximately eight million hospital stays from 1,000 hospitals from different states. It comprises 97 percent of the U.S. population. Hospitals that performed less than 100 deliveries per year were excluded from the study.
Overall low twin delivery volume
After excluding nine hospitals that did less than 100 annual deliveries, 547 hospitals with twin deliveries remained. Excluding twins who transferred into the hospitals for delivery, annual twin delivery volume in these hospitals ranged from 1 to 506. The researchers found an overall low twin delivery volume in the U.S. obstetric hospitals with a median annual twin delivery volume of 10 in the 547 included hospitals. The most frequent number of annual deliveries was 3 with 25 percent of hospitals performing between 1 and 4 twin deliveries per year. The highest volume hospitals performed between 33 and 506 annual twin deliveries. This highlights the range in variation of hospitals exposure to twin delivery.
Hospital’s culture affects c-section delivery rate
Contrary to the study’s hypothesis, twin cesarean delivery rates were not inﬂuenced by twin delivery volume. Rather, a hospital’s overall cesarean and vaginal birth after c-section (VBAC) rate was correlated with twin cesarean delivery rates. The lowest rates of twin cesarean delivery were found in hospitals with the lowest overall cesarean delivery rate and highest vaginal birth after c-section rate across all subgroups. These ﬁndings suggest that twin cesarean delivery rates are a product of a hospital’s general obstetric practice or culture surrounding vaginal birth more so than its twin delivery volume.