Premature newborns are 32% less likely to die if they are admitted to high volume neonatal units rather than low volume, according to new research.
The study, led by the University of Warwick and published in BMJ Open, analysed data from 165 neonatal units across the UK. It found babies born at less than 33 weeks gestation were 32% less likely to die if they were admitted to high volume units, compared to low volume.
For babies born at less than 27 weeks the effect was greater, with the odds of dying almost halved when they were admitted to high volume units, compared to low volume.
The research was led by Sam Watson from the University of Warwick's Medical School and Department of Economics.
He said: "One possible explanation for our results could be that those neonatal units delivering a greater volume of care provide the clinicians who work there with more experience. The first hours of these babies' lives can be crucial, which means it is essential to give them expert care at this time.
"It is also possible that economies of scale play a role, in that the larger and busier units have more resources to invest in technology and facilities. However more research is needed to tease out the possible explanations and inform policy effectively."
The research was carried out in collaboration with Imperial College London, University of Leicester and University College London.
The team analysed data for 20,554 babies born at less than 33 weeks and for 2,559 babies born at less than 27 weeks. Twenty-four per cent of the neonatal units were classified as high volume and 46.4% of infants born at less than 33 weeks were born in hospitals with a high volume neonatal unit.
For this study high volume neonatal units were defined as those that provide more than 3,480 care days to preterm babies per year. Several possible factors that could influence the statistical analysis were taken into account including age, birth weight and sex of the baby.
Fellow researcher Professor Neena Modi from the Department of Medicine, Imperial College London said: "Our research shows that neonatal units that are larger and busier in terms of the amount of care they provide to preterm babies are more likely to show better clinical outcomes for these vulnerable infants. This supports the networked approach that centralises the delivery of specialised neonatal care in high volume units and enables women at risk to be transferred to these units to receive the care they need."
There has been much debate about the organisation of critical care services for newborn babies, especially in relation to the volume and intensity of care units. In 2003 the UK created a model of networked, regionalised units to facilitate the transfer of preterm babies to higher care specialist units (NICUs), whilst also maintaining access to less specialist low volume units for those mothers and babies less at risk. These are now known as English Operational Delivery Networks. The results of this study support this approach but the researchers call for a need to further evaluate the effect of the transfers and to consider ways to improve procedures surrounding them.
Sam Watson said: "Our study indicates that ensuring very preterm babies, particularly those born at less than 27 weeks, are delivered in hospitals with high volume neonatal units improves their outcome, but there could be a knock-on effect on other patient groups if smaller neonatal units are closed. Babies who are not born so early but who are still vulnerable may have to travel far from home as a consequence and this is why further research is urgently needed."
Fellow researcher and professor in the Department of Economics at the University of Warwick, Wiji Arulampalam added: "This research underscores the importance of academic collaboration to bring together expertise from different fields of study. The study was made possible by combining medical expertise and statistical techniques used by economists. A standard statistical analysis would not have been able to identify the causal effect of the neonatal units' characteristics on the health outcomes for pre-term babies."
Fellow researcher at Warwick Medical School, Professor of Health Economics Stavros Petrou said: "This study uses an instrumental variables methodology to estimate the 'causal effects' of volume of neonatal care provided at the hospital of birth on infant outcomes. It accounted for both observed and unobserved confounding in a way that standard logistic regression doesn't, thereby demonstrating the added value of incorporating techniques used by economists in applied health research."
Notes to editors
1) Watson et al. 'The effects of designation and volume of neonatal care on mortality and morbidity outcomes of very preterm infants in England: retrospective population-based cohort study.' BMJ Open 2014. Paper is available here
2) Funding for the research came from Bliss and the Department of Economics at the University of Warwick.
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