Extremely growth-retarded infants: is there a viability centile?

BACKGROUND: It is known that extremely premature infants do less well than more mature infants, and this fact has led some countries to adopt a "cutoff for viability" using birth weight or gestation. Infants affected by intrauterine growth retardation are at additional risk of poor outcome. There are few data to inform decisions about viability and (dis)continuation of intensive care when both extreme prematurity and severe growth retardation are present.
OBJECTIVE: We focused on (1) premature infants affected by marked intrauterine growth retardation to determine if there was a cutoff weight centile below which the mortality sharply increased and (2) the short-term outcome of extremely premature and growth-retarded infants to determine a cutoff for viability.
METHODS: We evaluated preterm infants of 22-32 weeks' gestation if they were alive at the onset of labor and born to European mothers resident in the Trent (United Kingdom) health region between 1994 and 2003. Infants were categorized into 6 weight centiles, and infants in each category were assessed for survival to discharge from the neonatal unit, duration of respiratory support, length of stay in the neonatal unit, and the age at death in nonsurvivors.
RESULTS: We identified a total of 8228 infants who met the study criteria. Of these, 4448 infants were male, 6194 were from singleton pregnancies, and 2887 were born at < or = 28 completed weeks of gestation. Survival to discharge was markedly reduced in the infants born at < or = 28 weeks of gestation with a birth weight less than the 2nd centile. Stillbirth was inversely related to birth weight centile in infants born before 29 weeks of gestation.
CONCLUSIONS: The survival for infants born at < or = 28 weeks' gestation and having a birth weight in less than the 2nd centile is poor, and consideration should be given to modifying their management.