Trends in Bronchopulmonary Dysplasia among Extremely Preterm Infants in Japan, 2003–2016

Objective To investigate recent trends in bronchopulmonary dysplasia (BPD) and its risk factors among extremely preterm infants. Study design 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 2003-2016. We investigated the overall survival and prevalence of BPD at 36 weeks’ postmenstrual age and risk factors for developing BPD among the survivors. Results Among 19,370 infants, 2,244 (11.6%) died by 36 weeks’ postmenstrual age. The mortality rate decreased from 19.0% (99% confidence interval: 15.7%–22.8%) in 2003 to 8.0% (6.2%–10.3%) in 2016. Among 17,126 survivors, BPD developed in 7,792 (45.5%) infants, and its proportion significantly increased from 41.4% (36.5%–46.4%) in 2003 to 52.0% (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 > 4 weeks’ noninvasive positive pressure ventilation, chorioamnionitis, Conclusions The mortality rate of extremely preterm infants has declined, but the rate of BPD has increased in survivors between 2003-2016. Despite the decreasing duration of invasive ventilation over time, increasing rates of BPD suggest that differences in the patient population or other management strategies influence the development of BPD.