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Survival of very low birthweight and very preterm infants in a geographically defined population
1Department of Child Health, University of Wales College of Medicine, Cardiff, UK.
Insights
Survival rates for premature infants improve significantly with increasing postnatal age. Updated birthweight and gestation-specific data are crucial for accurate infant outcome predictions, especially in the first few days of life.
Area of Science:
- Neonatalogy
- Perinatal Epidemiology
- Public Health
Background:
- Infant survival rates for extremely low birthweight and preterm infants are critical indicators of neonatal care quality.
- Accurate prediction of infant outcomes requires up-to-date, population-specific data.
Purpose of the Study:
- To determine the 1-year survival rates for infants with birthweight <1500g or gestational age <32 weeks.
- To assess the impact of postnatal age on predicted infant survival.
Main Methods:
- A cohort analysis of 72,427 births in Wales (1993-94) was conducted.
- Population-based surveillance of mortality from 20 weeks gestation to 1 year of age was utilized.
- Birthweight- and gestation-specific infant mortality rates were calculated, along with the effects of postnatal age, gender, and multiple births.
Main Results:
- One-year survival for infants born at 24-25 weeks gestation was 35%, increasing to 95% at 30-31 weeks.
- Survival rates for infants weighing 500-699g was 18%, compared to 97% for those weighing 1300-1499g.
- Survival chances improved significantly with postnatal age; for infants at 24-25 weeks gestation, survival increased from 35% at birth to 78% at 4 weeks. Infant mortality was higher in males, with no effect from multiple pregnancies.
Conclusions:
- Birthweight- and gestation-specific survival rates are essential for predicting newborn outcomes.
- The rapid improvement in survival with increasing postnatal age highlights the need for regularly updated predictions, particularly in the early neonatal period.
Objective:
To determine in a geographically defined population 1 year survival of infants with a birthweight of less than 1500 g or gestational age less than 32 weeks, and to establish the effect of postnatal age on predicted survival.
Design:
Cohort analysis of 72,427 births to Welsh residents in 1993-94. Deaths were identified using the All Wales Perinatal Survey, a population-based surveillance of mortality between 20 weeks of gestation and 1 year of age.
Main Outcome Measures:
Birthweight- and gestation-specific infant mortality, and the effect of postnatal age, gender, and multiple pregnancy on predicted survival.
Results:
In normally formed infants 1 year survival at 24-25 weeks gestation was 35%, compared to 75% at 27-28 weeks, and 95% at 30-31 weeks. In infants with a birthweight of 500-699 g 1 year survival was 18% compared to 70% at 800-999 g, and 97% at 1300-1499 g. The chances of survival improved markedly with increasing postanatal age; at 24-25 weeks gestation it was 35% at birth, 50% at 12 h. 66% at 7 days and 78% at 4 weeks. Infant mortality was higher in males, but multiple pregnancy had no effect.
Conclusions:
Up-to-date birthweight- and gestation-specific survival rates are essential for predicting the outcome of a newborn infant. The rapid change in the chances of survival with increasing postnatal age emphasises especially the importance of revising the prediction as the infant gets older, particularly during the first few days of life.