322 - The impact of obstetric delivery volume on neonatal and pregnancy outcomes

Poster Number: 322
Publication Number: 322.1239

Background: Numerous clinical fields including surgical care and the care of high-risk infants exhibit volume-outcome associations. There is little information on the association between obstetric delivery volumes and adverse pregnancy outcomes, which can inform the development of optimal perinatal care systems.

Objective: To determine the association of annual hospital delivery volume and neonatal and pregnancy outcomes.

Design/Methods: We created a retrospective cohort of 2000-2020 birth certificates linked to death certificates and maternal and infant hospital discharge records of all births in CA, PA, MI, SC, and OR (N=12,086,389). The primary outcome was a delivery with a complication to either the pregnant patient (death; severe maternal morbidity; admission to the intensive care unit; infection, postpartum hemorrhage, or grade 3-4 laceration) or infant (death, unexpected severe complication of term gestation, including admission to the NICU; common complications of preterm birth). Delivery volume was grouped into either 5 categories ( < 1000, 1000-2000, 2000-4000, 4000-6000, 6000+) or by 250 birth units. Multivariable logistic regression models determined the association of annual hospital delivery volume with the primary outcome after adjusting for sociodemographic or medical factors, year, and hospital as a fixed effect to adjust for hospital factors such as case mix and resources that are consistent over the time period of the study.

Results: Hospitals with lower annual delivery volumes had a greater number of pregnancies with younger maternal age and Medicaid insurance but a lower proportion of preterm births (Table 1). In unadjusted analyses, the rate of primary and secondary outcomes were higher among hospitals with greater birth volume (Table 1). However, the risk-adjusted odds of an adverse pregnancy outcome in either the birth parent or infant were higher among hospitals with a delivery volume < 4000 (Figure 1). When examining volume in 250 birth increments, the highest risk-adjusted rates of adverse outcomes were seen in hospitals with < 1250 deliveries annually, with steadily decreasing rates until 5000 deliveries (Figure 2).

Conclusion(s): Lower obstetric delivery volume was associated with higher risk-adjusted rates of adverse maternal or infant outcomes, with the highest rates in hospitals with < 1250 deliveries annually. Identifying the resources, education, and training needed to support low volume hospitals, and matching needs of the patient with available hospital services, is necessary to optimize the health of pregnancy patients and infants in a fee-for-service payment system .