Temporal Trend and Risk Factors for Respiratory Distress Syndrome–Associated Neonatal Mortality in Preterm Infants: A Population-Based Study in a Middle-Income Country

Abstract

Objective This article aimed to report a temporal series of respiratory distress syndrome (RDS)-associated neonatal mortality rates in preterm live births in São Paulo state, Brazil, and to identify social, maternal, and neonatal characteristics associated with these deaths. Study Design This is a population-based study of all live births with gestational age (GA) between 22 and 36 weeks, birth weight ≥400 g, without congenital anomalies from mothers living in São Paulo state during 2004 to 2015. RDS-associated neonatal mortality was defined as death up to 27 days after birth with ICD-10 codes P22.0 or P28.0. RDS-associated neonatal mortality rate (annual percent change [APC] with 95% confidence intervals [95% CIs]) was analyzed by Prais–Winsten. Kaplan–Meier estimator identified the time after birth that the RDS-associated neonatal death occurred. Poisson's regression model compared social maternal and neonatal characteristics between preterm live births that survived the neonatal period and those with RDS-associated neonatal deaths, with results expressed in incidence rate ratio and 95% CI. Results A total of 645,276 preterm live births were included in the study, of which 612,110 survived and 11,078 had RDS-associated neonatal deaths. RDS-associated neonatal mortality rate was 17.17 per thousand preterm live births, with a decreasing annual trend (APC: −6.50%; 95% CI: −9.11 to −3.82%). The median time of these deaths was 48 hours after birth. The following risk factors for RDS-associated neonatal death were identified: maternal schooling ≤7 years (1.18; 1.09–1.29), zero to three prenatal care visits (1.25; 1.18–1.32), multiple pregnancy (1.24; 1.16–1.33), vaginal delivery (1.29; 1.22–1.36), GA 22 to 27 weeks (106.35; 98.36–114.98), GA 28 to 31 weeks (20.12; 18.62–21.73), male sex (1.16; 1.10–1.22), and 5-minute Apgar scores of 0 to 3 (6.74; 6.08–7.47) and 4 to 6 (3.97; 3.72–4.23). Conclusion During the study period, RDS-associated neonatal mortality rates showed significant reduction. The relationship between RDS-associated neonatal deaths and social, maternal, and neonatal factors suggests the need for perinatal strategies to reduce prematurity and to improve the initial management of preterm infants. Key Points