Hypertensive disease of pregnancy is associated with decreased risk for respiratory distress syndrome in moderate preterm neonates

Objective: To examine the effect of hypertensive disease of pregnancy (HDP) on the development of respiratory distress syndrome (RDS) in preterm neonates. Design: A retrospective cohort study. Setting: All neonatal intensive care units in New South Wales and the Australian Capital Territory. Patients: A total of 18,845 preterm neonates aged between 24 and 36 weeks gestation admitted to the units from 1998 to 2006 were included for study purpose. Exclusion criteria were multiple pregnancies, chorioamnionitis, antepartum hemorrhage and neonates who developed respiratory diagnoses other than RDS. Outcome measures: Effect of HDP on the development of RDS was measured. Results: A total of 1093 neonates from hypertensive and 2274 from normotensive pregnancies with complete datasets were included. The association between HDP and the development of RDS was modified by gestational age (HDP-by-gestational age interaction p value <0.0001). Therefore the cohort was divided into extreme (24-28 weeks gestation, n = 752), severe (29-32 weeks gestation, n = 1448) and moderate (33-36 weeks gestation, n = 1167) preterm groups. HDP was associated with a decreased risk of RDS in the moderate preterm group (OR: 0.68; 95% CI: 0.48-0.98, p = 0.04) and a non-significant change in risk for the severe preterm group. Almost all neonates in the extreme preterm group experienced RDS. Conclusion: HDP is associated with a lower risk of developing RDS in moderate preterm neonates. This could have clinical implications in terms of risk stratification for this group of neonates.