Changing outcome for infants of birth-weight 500-999 g born outside level 3 centres in Victoria

The aim of this study of extremely low birth-weight (ELBW, birth-weight 500-999 g) infants born in Victoria was to determine the changes between 3 distinct eras; 1979-80, 1985-87, and 1991-92, in the proportions who were born outside level 3 perinatal centres (outborn), the proportions of outborn infants who were transferred after birth to a level 3 neonatal unit, the survival rate for outborn infants, and sensorineural impairment and disability rates in outborn survivors. The proportion of ELBW Livebirths who were outborn fell significantly over successive eras, from 30.2% (106 of 351) in 1979-80, to 23.0% (129 of 560) in 1985-87, and to 15.6% (67 of 429) in 1991-92. Between 1979-80 and 1985-87, the proportions who were outborn fell predominantly in those of birth-weight from 800-999 g, whereas between 1985-87 and 1991-92 the proportions who were outborn fell predominantly in those of birth-weight 500-799 g. The proportions of outborn infants who were transferred after birth to a level 3 neonatal unit were similar in the 3 eras, at 49.1%, 38.0% and 41.2%, respectively. The survival rates for outborn infants were lower in each era than for infants born in a level 3 perinatal centre. Only 1 outborn infant not transferred after birth to a level-3 unit survived in any era. The survival rates for infants transferred after birth were similar in the first 2 eras, but rose significantly in 1991-92 (34.6%, 36.7% and 60.7%, respectively). The rates of sensorineural impairments and disabilities in survivors fell significantly between the first 2 eras, and remained low in the last era. It is pleasing that the proportion of tiny babies who were outborn fell significantly over time, reflecting increased referral of high-risk mothers to level 3 perinatal centres before birth. For ELBW outborn infants, survival prospects free of substantial disability are reasonable, but not as good as for those born in level 3 perinatal centres.