Effect of chorioamnionitis on postnatal growth in very preterm infants: a population-based study in Japan

Purpose There is growing evidence that preterm infants born to mothers with chorioamnionitis (CAM) have increased risk of various neonatal morbidities and long-term neurological disorders; however, the effect of CAM on postnatal growth remains insufficiently investigated. This study evaluated the effect of histological CAM on postnatal growth trajectories in very preterm infants using a nationwide neonatal database in Japan. Method A multicenter retrospective study was conducted using clinical data of 4220 preterm neonates who weighed <= 1500 g and were born at < 32 weeks of gestation between 2003-2017 (CAM group: n = 2110; non-CAM group: n = 2110). Z-scores for height and weight were evaluated at birth and 3 years of age. Univariable and multivariable analyses were conducted to evaluate the effect of histological CAM on Delta Z-scores of height and weight during the first three years with a stratification by infant sex and the stage of histological CAM. Results Multivariable analyses showed that histological CAM was associated with accelerated postnatal increase (Delta Z-score) in weight (beta coefficient [95% confidence interval]; 0.10 [0.00 to 0.20]), but not in height among females (0.06 [- 0.04 to 0.15]) and not in height and weight among males (0.04 [- 0.04 to 0.12] and 0.02 [- 0.07 to 0.11], respectively). An interaction analysis demonstrated no significant difference in the effect of histological CAM on the Delta Z-scores of height and weight during the first three years between male and female infants (height, p = 0.81; weight p = 0.25). Conclusions Intrauterine exposure to maternal CAM contributes to accelerated postnatal weight gain in female preterm infants during the first three years.