Length at birth z-score is inversely associated with an increased risk of bronchopulmonary dysplasia or death in preterm infants born before 32 gestational weeks: A nationwide cohort study

OBJECTIVE: We investigated whether the extent of fetal growth restriction (FGR) in terms of not only birth weight but length and head circumference at birth is correlated with an increased risk of bronchopulmonary dysplasia (BPD) in preterm infants. STUDY DESIGN: A total of 4,940 very low birth weight (VLBW) infants born between 23 and 31 weeks of gestation from 2013 to 2015 who were registered in the Korean Neonatal Network (KNN) database were enrolled. Infants with major congenital malformations and those with incomplete data were excluded. Z-scores for weight, length, and head circumference at birth were calculated from the Fenton 2013 growth curve. Multivariable logistic regression analysis was performed to determine whether the z-score for length at birth was associated with BPD or death before 36 postmenstrual weeks. RESULTS: A total of 4,662 VLBW infants were analyzed: 518 infants died before 36 postmenstrual weeks; 1,388 infants developed BPD. Decreased length at birth z-scores were significantly associated with an increased risk of BPD or death when adjusted for covariates (odds ratio (OR) 1.25 per 1-point decrease of length at birth z-score, 95% confidence interval (CI) 1.14–1.37). The association was particularly evident in infants born earlier than 29 weeks of gestation (OR 1.57, 95% CI 1.31–1.89 in infants born at 23–25 weeks; OR 1.24, 95% CI 1.09–1.42 in infants born at 26–28 weeks). CONCLUSION: Length at birth was inversely associated with an increased risk of BPD or death in VLBW infants born earlier than 32 weeks of gestation.