Trends in Bronchopulmonary Dysplasia Among Extremely Preterm Infants in Japan, 2003-2016

To investigate recent trends in bronchopulmonary dysplasia (BPD) and its risk factors among extremely preterm infants. Demographic and clinical data were reviewed for 19 370 infants born at 22-27 weeks of gestation registered in the affiliated hospitals of the Neonatal Research Network of Japan between 2003 and 2016. We investigated the overall survival and prevalence of bronchopulmonary dysplasia (BPD) at 36 weeks’ postmenstrual age and risk factors for developing BPD among the survivors. Among 19 370 infants, 2244 (11.6%) died by 36 weeks' postmenstrual age. The mortality rate decreased from 19.0% (99% CI, 15.7%-22.8%) in 2003 to 8.0% (99% CI, 6.2%-10.3%) in 2016. Among 17 126 survivors, BPD developed in 7792 (45.5%) infants, and its proportion significantly increased from 41.4% (99% CI, 36.5%-46.4%) in 2003 to 52.0% (99% CI, 48.2%-55.9%) in 2016. A multivariable analysis of the survivors showed a positive association of BPD with ≥4 weeks' supplemental oxygen or invasive ventilation, birth weight