Low Apgar score and mortality in extremely preterm neonates born in the United States

Aim: To investigate the relationship between low Apgar score and neonatal mortality in preterm neonates. Methods: Infant birth and death certificate data from the US National Center for Health Statistics for 2001-2002 were analysed. Primary outcome was 28-day mortality for 690 933 neonates at gestational ages 24-36 weeks. Mortality rates were calculated for each combination of gestational age and 5-min Apgar score. Relative risks of mortality, by high vs. low Apgar score, were calculated for each age. Results: Distribution of Apgar scores depended on gestational age, the youngest gestational ages having higher proportions of low Apgar scores. Median Apgar score ranged from 6 at 24 weeks, to 9 at 30-36 weeks gestation. The relative risk of death was significantly higher at Apgar scores 0-3 vs. 7-10, including at the youngest gestational ages, ranging from 3.1 (95% confidence interval 2.9, 3.4) at 24 weeks to 18.5 (95% confidence interval 15.7, 21.8) at 28 weeks. Conclusion: Low Apgar score was associated with increased mortality in premature neonates, including those at 24-28 weeks gestational age, and may be a useful tool for clinicians in assessing prognosis and for researchers as a risk prediction variable.