Skip Navigation U.S. Department of Health and Human Services
Agency for Healthcare Research Quality
Archive print banner

Children's Health

This information is for reference purposes only. It was current when produced and may now be outdated. Archive material is no longer maintained, and some links may not work. Persons with disabilities having difficulty accessing this information should contact us at: Let us know the nature of the problem, the Web address of what you want, and your contact information.

Please go to for current information.

Studies examine hospital mortality rates and long-term outcomes of very low birthweight babies

Babies who are extremely low birthweight (ELBW, 1.1 to 2.2 pounds) and very low birthweight (VLBW, less than 3.3 pounds) are at greater risk of dying or developing neurodevelopmental problems than babies who weigh more at birth. Two recent studies supported by the Agency for Healthcare Research and Quality examined hospital mortality and school difficulties among VLBW children.

The first study suggests that the number of VLBW babies saved could be increased if they were referred to hospitals based on the hospitals' past neonatal intensive care unit (NICU) mortality rates rather than the volume of VLBW babies they treat. The second study finds that school-aged ELBW children are burdened by childhood disability, school-related difficulties, and increased use of special educational resources. Both studies are discussed here.

Rogowski, J.A., Horbar, J.D., Staiger, D.O., and others (2004, January). "Indirect vs. direct hospital quality indicators for very low-birth-weight infants" (AHRQ grants HS10328, HS13371). Journal of the American Medical Association 291(2), pp. 202-209.

The type of medical care VLBW infants receive and their outcomes vary markedly among different NICUs. Some groups recommend that these at-risk babies be referred to high-volume NICUs that treat an average of 15 babies daily. However, this study suggests that many more infant lives could be saved if referrals were based on a hospital's past NICU mortality rates for VLBW infants rather than the volume of VLBW babies treated.

The investigators examined in-hospital deaths of 94,110 VLBW infants born from 1995-2000 in 333 hospitals with NICUs. The hospitals were included in the Vermont Oxford Network (VON). The VON data include detailed clinical and treatment information on all VLBW infants cared for by network hospitals and represent about 40 percent of the NICUs and 50 percent of the VLBW infants born in the United States.

In hospitals with less than 50 annual admissions of VLBW infants, an additional 10 admissions were associated with an 11 percent reduction in mortality. However, annual NICU volume, NICU level, and other hospital characteristics explained at most 16 percent of the variation in infant mortality across sampled hospitals.

In contrast, hospitals in the lowest mortality quintile between 1995 and 1998 were found to have 36 percent lower mortality rates in 1999-2000, and hospitals in the highest mortality quintile between 1995 and 1998 had 37 percent higher mortality rates in 1999-2000. Based on these estimates, a referral strategy that moved all infants out of the lowest-ranked 20 percent and into the middle 60 percent of VON hospitals in 1999-2000 would result in 11 lives saved annually based on NICU volume history and 115 lives saved annually based on NICU past mortality rates.

Saigal, S., den Ouden, L., Wolke, D., and others (2003, October). "School-age outcomes in children who were extremely low birth weight from four international population-based cohorts" (AHRQ grant HS08385). Pediatrics 112(4), pp. 943-950.

Once ELBW children reach school age, they experience serious school difficulties, whether they live in the United States, Canada, Bavaria, or Holland. The researchers followed 436 ELBW survivors from the four countries longitudinally from birth. They collected psychometric data that included at least one measure of cognitive status and one measure of achievement from surveys administered to the children between 8 and 11 years of age. The researchers compared these data with measures based on reference norms within each country and obtained information on special education assistance and grade repetition from the parents.

Overall, the prevalence of total neurosensory impairments (cerebral palsy, deafness and blindness, and mental retardation) was similar for New Jersey, Ontario, and Bavaria (22, 27, and 25 percent, respectively) and lowest for Holland (11 percent). More than half of all ELBW groups required special educational assistance and/or repeated a grade. The proportion of children who performed within the normal range were as follows: IQ, between 44 and 62 percent; reading, between 46 and 81 percent; arithmetic, between 31 and 76 percent; and spelling, between 39 and 65 percent.

Thus, the impact on society, on families, and on the long-term future of ELBW children is similar in Western countries providing neonatal intensive care to ELBW infants. A separate study by these investigators found behavioral difficulties to be another major concern at school age in ELBW children in all four countries. To determine whether and to what extent these findings are applicable to current survivors of neonatal intensive care requires further investigation.

Return to Contents
Proceed to Next Article

The information on this page is archived and provided for reference purposes only.


AHRQ Advancing Excellence in Health Care