Commentary: Does patient volume matter for low-risk deliveries?

Ciaran S Phibbs

Veterans Affairs Palo Alto Health Care System and Stanford University.

Health Economics Resource Center (152), VA Medical Center, 795 Willow Road, Menlo Park, CA 94025, USA. E-mail: cphibbs{at}stanford.edu

That there is a volume-outcome relationship for deliveries, and that mortality is lower for births that occur in hospitals with higher level neonatal intensive care units (NICU) is well established. Numerous studies have found this relationship for all births,1–4 or selected groups of higher risk cases.5–8

Using all births in the German State of Hesse for a 10-year period, the study by Heller et al.9 extends the volume-outcome, level of care analysis to low-risk births. The perinatal care system in Hesse is highly regionalized; over 90% of infants with a birthweight <1500 g (VLBW) are born in perinatal centres. Yet, even within this highly regionalized system the authors found that compared to births that occurred in high-volume delivery services, births occurring in hospitals with lower-volume delivery services had a 1.5- to 3-fold higher risk of mortality. The implications are a dramatic change from the past policy of regionalizing just high-risk deliveries. If replicated, these results would indicate that deliveries should be concentrated in high-volume facilities to the extent it is geographically possible. They enhance the case for increased regionalization, especially in countries such as the US with fragmented perinatal systems.10 As the authors correctly note, their findings raise significant policy questions and more study is needed before there are any changes in policy.

The Heller study was carefully done. They limited their analysis to infants with a birthweight >=2500 g, excluding those infants with a documented congenital anomaly as a cause of death. They only counted deaths that occurred during delivery or within 7 days of birth. Since the regionalized system works so well for VLBW infants, it is likely that it works well for most previously identified high-risk deliveries. Thus, it is unlikely that the results are due to previously identified high-risk deliveries occurring at the low-volume hospitals. The study did not report the causes of death, but most of the deaths included in the analyses are likely related to acute obstetric emergencies. The authors erred on the side of caution in their analyses, with the likely effect being to underestimate the actual effect of patient volume. Importantly, they could not identify normal birthweight deliveries antenatally referred to a perinatal centre for a high-risk condition that was not a lethal congenital anomaly. The inclusion of time of day of delivery also probably contributes to an underestimate of the true effect of patient volume; some of the time of day effect is probably driven by the ability to respond to emergencies.

The ability to identify high-risk cases is not perfect and some complications occur too late in the delivery process to subsequently move the delivery to a high-risk facility. Thus, some high-risk births will always occur at low-risk delivery services. The authors posit that the most likely cause of the results is the response time to medical emergencies at the lower-volume hospitals. While I am not familiar with the organizational details of care in Hesse, since these facilities focus on the care given to low-risk cases, it is likely that they are not as prepared to respond to medical emergencies as the perinatal centres. Most will not have 24-hour dedicated obstetric anaesthesia coverage and may lack continuous obstetric coverage. Further, many of these units will not be continuously staffed with the skilled personnel necessary for optimal neonatal resuscitation. Thus, it will take longer to perform emergency c-sections and to resuscitate newborns in circumstances where a few minutes makes a big difference. Since the availability of these personnel is likely to be inversely related to delivery volume, this also provides a plausible explanation for the volume gradient.

While this study indicates that lives could be saved if all births were concentrated in high-volume tertiary centres, caution is needed before making such a radical change to the health care system. Geographical access to delivery services needs to be considered. In larger urban areas it is clearly possible to concentrate deliveries in a few large delivery services with minimal added travel for patients. But, in smaller urban, semi-rural, and rural areas this could cause considerable added travel to reach delivery hospitals, which could adversely effect outcomes. Low-volume delivery services would need to be retained in some areas to maintain reasonable geographical access. Additional research is needed to determine how to make the decisions about trading off added travel distance with high delivery service volume. We also need to determine how large delivery services should be, the 1500 deliveries per year cutoff that Heller et al. used is not that large a delivery service.

Even in urban areas, the change to concentrate deliveries at a limited number of hospitals would be a major change from the current delivery system. Before any such change could be recommended, this study will need to be replicated and additional research is needed to determine the cause of the mortality differences. It would be wise to explore if there are any actions that can be taken to reduce the mortality differences across settings. Given that much of the mortality difference is probably due to response times for the unexpected emergencies, are there any organizational changes that could improve response times in smaller delivery services?

Even if the Heller et al. results are replicated, policy makers would be well advised to move slowly; shifting as many deliveries as geographically possible to tertiary centres would represent a massive shift of patients. In many areas the existing tertiary centres may not have the physical capacity to accommodate all of the additional deliveries. We must also consider that while the relative risk of mortality is fairly large, the baseline risk in this population is very low, so the number of potential lives saved is small. Any efforts to concentrate low-risk deliveries should first be tried in the most densely populated urban areas where it is most feasible. The effects should be studied to see if the actual gains match the expected gains, and to measure the costs or savings of such a policy.

References

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2 Paneth N, Kiely JL, Wallenstein S, Susser M. The choice of place of delivery. Effect of hospital level on mortality in all singleton births in New York City. Am J Dis Child 1987;141:60–64.[Abstract]

3 Powell SL, Holt VL, Hickok DE, Easterling T, Connell FA. Recent changes in delivery site of low-birth-weight infants in Washington: Impact on birth weight-specific mortality. Am J Obstet Gynecol 1995; 173:1585–92.[ISI][Medline]

4 Yeast JD, Poskin M, Stockbauer JW, Shaffer S. Changing patterns in regionalization of perinatal care and the impact on neonatal mortality. Am J Obstet Gynecol 1998;178:131–35.[ISI][Medline]

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6 Phibbs C, Bronstein J, Buxton E, Phibbs R. The effect of patient volume and level of care at the hospital of birth on neonatal mortality. JAMA 1996;276:1054–59.[Abstract]

7 Cifuentes J, Bronstein JM, Phibbs CS, Phibbs RH, Schmitt SK, Carlo WA. Mortality according to level of neonatal care at hospital of birth in low birth weight infants. Pediatrics 2002:109:745–51.[Abstract/Free Full Text]

8 Ozminkowski RJ, Wortmann PM, Dietrich R. Inborn/outborn status and neonatal survival: A meta-analysis of non-randomized studies. Stat Med 1988;7:1207–21.[ISI][Medline]

9 Heller G, Richardson DK, Schnell R, Misselwitz B, Künzel W, Schmidt S. Are we regionalized enough? Early-neonatal deaths in low-risk births by the size of delivery units in Hesse, Germany 1990–1999. Int J Epidemiol 2002;31:1038–45.[Abstract/Free Full Text]

10 Gagnon D, Allison-Cooke S, Schwartz RM. Perinatal Care: the threat of deregionalization. Pediatr Ann 1988;17:447–52.[ISI][Medline]





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