Gestational age-specific neonatal mortality in Hong Kong: a population-based retrospective study.

Background: The neonatal period is the most vulnerable period during childhood, with the risk of death being the highest even in developed countries/regions. Hong Kong's neonatal mortality (1‰) is among the world's lowest and has remained similar for 15 years. This study aimed to explore neonatal deaths in Hong Kong in detail and determine whether neonatal mortality is reducible at such a low level.

Methods: Live births in public hospitals in Hong Kong during 01 Jan 2006-31 Dec 2017 were included. Relevant data were extracted from the electronic medical records. Gestational age-specific mortality was calculated, and the trends were analyzed using the Cochran-Armitage trend test. Causes of death were summarized, and risk factors were identified in multivariate logistic regression analysis.

Results: In 490,034 live births, 755 cases (1.54‰) died during the neonatal period, and 293 (0.6‰) died during the post-neonatal period. The neonatal mortality remained similar overall (P = 0.17) and among infants born at 24-29 weeks' gestation (P = 0.4), while it decreased in those born at 23 (P = 0.04), 30-36 (P < 0.001) and ≥ 37 (P < 0.001) weeks' gestation. Neonates born at < 27 weeks' gestation accounted for a significantly increased proportion among cases who died (27.6% to 51.9%), with hemorrhagic conditions (24%) being the leading cause of death. Congenital anomalies were the leading cause of death in neonates born ≥ 27 weeks' gestation (52%), but its cause-specific mortality decreased (P = 0.002, 0.6‰ to 0.41‰), with most of the decrease attributed to trisomy 13/18 and multiple anomalies.

Conclusion: Reduction of neonatal mortality in developed regions may heavily rely on improved quality of perinatal and neonatal care among extremely preterm infants.