Published online August 1, 2006
PEDIATRICS
Vol. 118
No. 2
August 2006, pp.
818-819
(doi:10.1542/peds.2006-1397)
Is There a Viability Centile for Extremely Growth-Retarded Infants?
Esther Rieger-Fackeldey, MD, PhD
Department of Women’s and Children’s Health, Section for Pediatrics, and Department of Neuroscience, Uppsala University, Uppsala, Sweden; Neonatology, Perinatal Center, Klinikum Grosshadern, Ludwig Maximilian University, Munich, Germany
Growth-restricted preterm infants have increased mortality and morbidity.1–5 Among them, the very immature infants with gestational ages <27 completed weeks’ gestation run a high risk for adverse outcomes.6 Infants with birth weights <500 g are often considered to be nonviable, and their outcome varies to a great extent.7–11 Although the chances of survival of extremely low birth weight infants have improved in recent years,12 there are not enough data available to answer the question "how small is too small?"
A study by Kamoji et al,13 published in this issue of Pediatrics, has addressed this topic by testing the hypothesis that there is a viability weight centile over all gestational-age groups in preterm infants.
The findings of this study on short-term outcome indicate that the survival for infants born at 
28 weeks’ gestation weighing less than the 2nd centile is poor. This effect was not seen in infants born after 28 weeks. Stillbirth occurred more frequently in infants born before 29 completed weeks of gestation in the lowest centiles. Lengths of stay and duration of respiratory support were used as a marker of resource use; both were inversely related to birth weight centile for infants born before 28 completed weeks of gestation.
The strengths of this study are the use of a population-based cohort, the size of the cohort of 8228 infants, the inclusion of all infants alive at the onset of labor and of all stillborn infants, and the application of a gestational-age criterion. In fact, there are few comparable data available from Europe. In the lower-centile groups of infants below 28 weeks, however, the numbers of infants are rather small. Changes occurring by chance could have occurred in such small numbers. A trend to higher mortality of the low-centile categories in the group of infants below 28 weeks might be present but not detectable. The numbers of infants and mortality should be given by the exact gestational age in addition to the 2 big strata to show the clinician how many infants of extremely low gestational age were included. Additional weaknesses include the lack of information on prenatal risk factors, antenatal steroids, obstetric management, mode of resuscitation in the delivery room, causes of death, and withdrawal of intensive care. Knowledge of obstetric and neonatal management is important for obtaining valid mortality data.
Kamoji et al have identified the 2nd weight centile as a "viability centile" in preterm infants in their study including data from 2 huge epidemiologic databases. Information on obstetric and neonatal management should be implemented in such databases to strengthen the results of studies on mortality and morbidity using those databases. It would be interesting to determine if the data are confirmed in larger nonepidemiologic databases (National Institute of Child Health and Human Development, Vermont Oxford Network). Long-term follow-up data are needed; a "viability centile" might be a "poor-prognosis centile." Thus, the best treatment approach for extremely growth-restricted preterm infants at low gestational ages still needs to be defined.
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FOOTNOTES
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Accepted May 23, 2006.
Address correspondence to Esther Rieger-Fackeldey, MD, PhD, Neonatology, Perinatal Center, Klinikum Grosshadern, Ludwig Maximilian University, Marchioninistrasse 15, D-81377 Munich, Germany. E-mail: esther.fackeldey{at}kbh.uu.se
The author has indicated she has no financial relationships relevant to this article to disclose.
Opinions expressed in these commentaries are those of the authors and not necessarily those of the American Academy of Pediatrics or its Committees.
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