Mortality and morbidity of extremely low birth weight infants in Hong Kong, 2010-2017: a single-centre review

Background: Extremely low birth weight (ELBW) infants exhibit high rates of mortality and morbidity. We retrospectively assessed factors associated with mortality and morbidity among ELBW infants. Methods: Perinatal demographic data were reviewed for all ELBW infants born between 2010 and 2017 at a tertiary neonatal unit. Results: For non-survivors (21% of ELBW infants) and survivors, the median gestational ages were 24.1 and 26.2 weeks, respectively, and median birth weights were 650 g and 780 g, respectively (all P<0.001). Regression analyses showed that non-survival was positively associated with lower gestational age (adjusted odds ratio [aOR] = 6.71 for every 1-week decrease; 95% confidence interval [CI] = 1.7326.00; P=0.006) and grade 3 or 4 intraventricular haemorrhage (aOR = 29.23; 95% CI=1.39-613.84; P=0.030); non-survival was negatively associated with the presence of bronchopulmonary dysplasia (aOR=0.01; 95% CI = < 0.001-0.23; P=0.005); length of neonatal intensive care unit stay for survivors was positively associated with the presence of necrotising enterocolitis (B-coefficient = 89.60; 95% CI=43.86135.34; P < 0.001); and length of hospital stay for survivors was positively associated with the presence of necrotising enterocolitis (B-coefficient=2.08; 95% CI=0.43-3.73; P=0.015) and a low Apgar score at 1 minute (B-coefficient=-0.63; 95% CI=-1.04 to -0.22; P=0.003). Conclusion: Extremely low birth weight infants exhibited significant mortality and morbidity; there was no survival prior to 23.6 weeks' gestation or below 550 g birth weight. The presence of grade 3 or 4 intraventricular haemorrhage was independently associated with non-survival. Survivors were significantly more likely to exhibit bronchopulmonary dysplasia; survivors with necrotising enterocolitis were more likely to require longer stays in the neonatal intensive care unit and in hospital.