Changing long-term outcomes for infants 500-999 g birth weight in Victoria, 1979-2005
L W Doyle1, G Roberts, P J Anderson
1Department of Obstetrics & Gynaecology, The Royal Women's Hospital, 20 Flemington Road, Parkville, VIC 3052, Australia. lwd@unimelb.edu.au
Insights
Survival rates for extremely low birthweight (ELBW) infants have plateaued, but their neurosensory outcomes have improved. This study compares 2005 ELBW survivors to earlier cohorts and term controls.
Area of Science:
- Neonatalogy
- Perinatal Epidemiology
- Developmental Pediatrics
Background:
- Extremely low birthweight (ELBW) infants (500-999 g) face significant survival and developmental challenges.
- Historical trends show improvements in ELBW infant survival and outcomes.
- Contemporary outcomes require evaluation against previous cohorts and term controls.
Purpose of the Study:
- To assess the 2-year survival and neurological outcomes of ELBW infants born in Victoria in 2005.
- To compare these outcomes with term-born controls.
- To contrast the 2005 ELBW cohort with historical ELBW cohorts from earlier eras.
Main Methods:
- Population-based cohort study design.
- Inclusion of all live-born ELBW infants (500-999 g) without lethal malformations in Victoria in 2005 (n=257).
- Inclusion of randomly selected term, normal birthweight controls (n=220) and historical ELBW cohorts from 1979-1980, 1985-1987, 1991-1992, and 1997.
Main Results:
- The 2-year survival rate for ELBW infants in 2005 was 66.9%, a decrease compared to 75.2% in 1997 (p=0.046), with no significant difference after confounder adjustment.
- Rates of blindness, severe developmental delay, and severe disability were significantly lower in 2005 ELBW survivors compared to previous eras.
- Quality-adjusted survival rates showed a non-significant difference between the 2005 and 1997 ELBW cohorts (-3.8%, p=0.32).
Conclusions:
- Survival rates for extremely low birthweight infants in Victoria have plateaued since the late 1990s.
- Neurosensory outcomes for survivors of extremely low birthweight infants have improved in 2005.
- The findings highlight a shift towards improved quality of survival despite stabilized survival rates.
Objective:
To determine the survival and neurological outcome at 2 years of age of extremely low birthweight (ELBW, birth weight 500-999 g) infants born in the state of Victoria compared with term controls, and contrasted with ELBW cohorts from previous eras.
Design And Setting:
A population-based cohort study of consecutive ELBW infants born during 2005 in the state of Victoria, and also in 1979-1980, 1985-1987, 1991-1992 and 1997.
Participants:
All 257 live births free of lethal malformations weighing 500-999 g in 2005, 220 randomly selected term, normal birthweight (birth weight >2499 g) controls, and equivalent cohorts born in earlier eras.
Main Outcome Measures:
Survival rates and quality-adjusted survival rates at 2 years of age, contrasted between cohorts.
Results:
Of 257 ELBW live births in 2005, 66.9% survived to 2 years of age, significantly lower than the survival rate of 75.2% for 1997 (odds ratio (OR) 0.67, 95% CI 0.45 to 0.99, p=0.046), but not after adjustment for confounders of birth weight, gestational age and gender (adjusted OR 0.73, 95% CI 0.46 to 1.16, p=0.18). This was a reversal of the steady increase in survival rates up to 1997. Rates of blindness, severe developmental delay and severe disability were significantly lower in 2005 than in ELBW survivors from previous eras. Consequently the difference in the quality-adjusted survival rates between 2005 and 1997 was only -3.8% (95% CI -11.4% to 3.7%, p=0.32).
Conclusions:
Regional survival rates for ELBW infants have plateaued since the late 1990s, but the neurosensory outcome in survivors has improved in 2005.
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