Impact of maternal age on neonatal outcomes among very preterm infants admitted to Chinese neonatal intensive care units: a multi-center cohort study

Background: The percentage of advanced maternal age (aged over 35 years) mothers has been rising across the world, the evidence of maternal age on neonatal outcomes from low- and middle-income countries is scarce. Our objective was to evaluate the effect of maternal age on mortality and major morbidity among very preterm infants admitted to Chinese neonatal intensive care units. Methods: Data from a retrospective multi-center cohort of all complete care very preterm infants admitted to 57 neonatal intensive care units that participated in the Chinese Neonatal Network from January 1st to December 31st, 2019 were analyzed. Neonatal outcomes including mortality or any major morbidity, defined as necrotizing enterocolitis stage 2 or 3, moderate & severe bronchopulmonary dysplasia, severe intraventricular hemorrhage, cystic periventricular leukomalacia, severe retinopathy of prematurity, or sepsis. A multiple logistic regression model was constructed to analyze the independent association between maternal age and neonatal outcome. Results: Among 7,698 eligible newborns, 80.5% of very preterm infants were born to mothers between the ages of 21 and 35 years, with 18.0% born to mothers >35 years and 1.5% born to mothers <21 years. Higher rates of maternal hypertension, maternal diabetes, cesarean deliveries, antenatal steroid usage were noted as maternal age increased. The proportion of prenatal care, cesarean section, antenatal steroid usage and inborn for very preterm infants born to mothers <21 years was lower than those of mothers of other ages. Compared to the ages of 21-35 years group, the odds of severe intraventricular hemorrhage (adjusted odd ratio: 2.00, 95% CI: 1.08-3.71) was significantly higher in the ages of 15-20 years group. Increasing maternal age was associated with higher rates of small for gestational age and lower birth weight of very preterm infants, but no correlation between advanced maternal age and very preterm infants mortality or major morbidity. Conclusions: Among very preterm infants, increasing maternal age was associated with higher rates of small for gestational age but not neonatal mortality or major morbidity. Young maternal age may increase the risk of severe intraventricular hemorrhage of very preterm infants.