Objectives: To determine the impact of maternal and fetal intrauterine inflammatory responses (chorioamnionitis and umbilical vasculitis) on the development of neonatal respiratory distress syndrome (RDS) in preterm infants.
Design, setting and subjects: The study included all infants <30 weeks' gestation born at the Royal Prince Alfred Hospital, Sydney, Australia, and admitted to neonatal intensive care from 1992 to 2001. Those without placental examination were excluded. Antenatal and perinatal data were extracted from prospectively kept hospital databases and correlated with the independent, central neonatal database. Placentae were examined prospectively using a standardised, semi-quantitative method.
Main outcome measure: A diagnosis of neonatal RDS.
Results: There were 766 eligible babies and 724 (94.5%) had placental examination. The mean (SD) gestational age of the cohort was 27.1 (1.6) weeks. Antenatal maternal steroids were given to 93.6%. Histological chorioamnionitis alone was evident in 19.1% of infants, and chorioamnionitis with umbilical vasculitis in 30.2%. Regression analysis showed that increasing gestational age (adjusted odds ratio (OR) 0.72, 95% CI 0.64 to 0.81), chorioamnionitis (adjusted OR 0.49, 95% CI 0.31 to 0.78), and chorioamnionitis with umbilical vasculitis (adjusted OR 0.23, 95% CI 0.15 to 0.35) were associated with a significant reduction in RDS. Factors associated with increased odds of RDS were multiple gestation (twin or triplet pregnancies), pregnancy-induced hypertension and an Apgar score <4 at 1 minute.
Conclusions: Maternal and fetal intrauterine inflammatory responses are both protective for RDS. The presence of chorioamnionitis with umbilical vasculitis is associated with a markedly greater reduction of RDS than chorioamnionitis alone.