Preterm infant mortality lower at high volume neonatal centers
1. Infants less than 27 weeks gestation born at high volume centers had lower neonatal mortality and lower any in-hospital mortality, regardless of center’s tertiary level status.
2. Despite reorganization of perinatal centers in England, volume of care provided at center remains an important determinant of premature neonatal outcomes.
Evidence Rating Level: 2 (Good)
Study Rundown: Since reorganization of neonatal care in England in 2003, there has been an increase in proportion of preterm infants born at tertiary care and high volume neonatal units, with unknown effects on outcomes. The study analyzed data from over twenty thousand preterm infant births, looking at various causes of morbidity and mortality. Researchers found that very premature infants, <27 weeks, born at high volume centers had lower neonatal and any in-hospital mortality, independent of tertiary level designation, with no significant differences in morbidity. Strengths of the study include data from a comprehensive, centralized database covering the vast majority of neonatal units in England. In addition, the researchers corrected for confounding social factors such as resource deprivation by utilizing two different regression models. Some weaknesses of the study include retrospective analysis of the data and the inability to quantify the effects of patient geographical constraints and unfulfilled in utero transfer requests. These limitations likely attenuate the observed benefits of birthing at high volume centers.
The study contributes to data for neonatal care referrals, resource organization, and treatment guidelines by demonstrating the benefits of higher case volume over tertiary status. It also quantifies, for the first time since the reorganization of perinatal centers in England, mortality benefits of birthing very preterm infants at high volume centers, allowing for outcomes comparison with similar studies performed elsewhere in Europe and America.
Click to read the study, published today in BMJ
Relevant Reading: Perinatal Regionalization for Very Low-Birth-Weight and Very Preterm Infants
In-Depth [retrospective cohort]: This study sought to elucidate the effects of volume and classification of level of care of neonatal units on premature infant mortality in England. Data from 20,554 preterm infants born at <33 weeks over a three year period between 2009 and 2011 from the National Neonatal Research Database was analyzed. Infants were categorized based on age, <27 weeks or 27 to <33 weeks, and place of birth, specifically tertiary or high volume neonatal units. High volume centers were defined based on being in the top quartile of the sample in volume or as having greater than 100 very low birth weight deliveries per year. High volume centers accounted for 46.4% of all preterm births compared to 46.1% at tertiary centers, with 37.2% births occurring at a center classified as both. The data was analyzed by both standard logistic regression and instrumental variables logistic regression. While standard logistic regression showed significant mortality benefits across both types of centers, instrumental variables logistic regression, which adjusts for unknown confounding variables, found no mortality benefits for tertiary care centers. High volume centers provided improved neonatal mortality (OR 0.54, CI95% 0.33-0.87) and any in-hospital mortality (OR 0.51, CI95% 0.33-0.79) for infants born at <27 weeks. Interestingly, the incidence of bronchopulmonary dysplasia was increased in tertiary neonatal units, for infants born at <33 weeks, and high volume units, for infants born at <27 weeks. Other morbidities evaluated but which showed no statistical significance included necrotizing enterocolitis, retinopathy of prematurity, and postmenstrual age at discharge – a proxy for hospital stay.
Image: PD
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