Table 3.

Mortality rates of extremely low birth weight infants (≤500 g, 401–1,000 g).

Author	Country	Year(s)	Methods	Age of infants	Mortality outcome	Reasons for death
Keir et al. (21)	Australia	2005–2010	Data for 36 extremely low birth weight infants (≤500 g), including 26 NICU patients, born at a tertiary hospital	GA of ≥22 weeks Mean GA of the 12 deceased infants: 24.4 ± 1.4 weeks Median age at death: 20 days	46% (12/26)	NEC (n = 2, 17%), fulminating NEC (n = 2, 17%), recurrent NEC/multiple cardiorespiratory arrests (n = 1, 8%), progressive lactic acidosis – unresponsive to treatment (n = 1, 8%), severe lung disease (n = 1, 8%), respiratory failure/sepsis (n = 1, 8%), massive liver necrosis and fibrosis – etiology unclear (n = 1, 8%), severe irrecoverable chronic lung disease (n = 1, 8%), lower limb gangrene/cardiorespiratory arrest (n = 1, 8%), bilateral grade IV IVH (n = 1, 8%)
Tagare et al. (26)	India	December 1, 2006–April 30, 2008	Data for 87 extremely low birth weight infants admitted to a level III NICU	Mean GA of deceased infants: 27.2 weeks (range: 26.6–27.8)	45.9% (40/87)	Pulmonary hemorrhage (n = 10, 25%), RDS (n = 9, 22.5%), IVH (n = 9, 22.5%), sepsis (n = 8, 20%), NEC (n = 1, 2%), BPD (n = 1, 1%), pneumothorax (n = 1, 1%)
Alleman et al. (38)	United States of America	2006–2009	Data for 5,418 extremely low birth weight (401–1,000 g) infants born at 16 Neonatal Research Network centers	GA of 22–28 weeks	Median mortality of all infants in the 16 centers: 34% (~1,842/5,418) (range: 11–53%) Median mortality of infants <25 weeks GA in the 16 centers: 63% (range: 28–90%) Median mortality of infants ≥25 weeks GA in the 16 centers: 16% (range: 7–26%)	Not listed

BPD, bronchopulmonary dysplasia; g, grams; GA, gestational age; IVH, intraventricular hemorrhage; N, number; NEC, necrotizing enterocolitis; NICU, neonatal intensive care unit; RDS, respiratory distress syndrome.