Risk factors for respiratory distress syndrome among high-risk early-term and full-term deliveries

Objective: To identify whether risk factors for respiratory distress syndrome (RDS) differ between early-term and full-term births.

Study design: This is a secondary analysis of a large NIH-funded retrospective cohort study including patients who delivered at a tertiary-care obstetric hospital between January 2002 and March 2013 with comorbid diabetes, hypertensive disorders, and/or fetal growth restriction (FGR). Pregnancies complicated by severe preeclampsia and multifetal gestations were excluded. Maternal characteristics, delivery information, and neonatal information were abstracted by trained clinicians blinded to the comorbidity leading to study inclusion. In this secondary analysis of the infant health outcomes of pregnancies with one or more of the qualifying conditions, risk factors for RDS among neonates born early term (37w0d-38w6d gestation) were compared to risk factors for RDS among full-term neonates (39w0d-40w6d).

Results: Among 10,532 singleton newborns, there were 99 cases of early-term RDS (0.94%) and 95 cases of full-term RDS (0.90%). Maternal demographics were similar between those with and without RDS in both groups. Among early-term infants, lower gestational age, presence of meconium, non-spontaneous labor, and cesarean delivery were positively associated with RDS, whereas hypertensive disorders, diabetes, FGR, and many other comorbid delivery conditions were not. The strongest risk factor for RDS among early-term infants was delivery via cesarean (RR 1.98, 95% CI 1.31, 3.01). Among full-term neonates, cesarean delivery was also positively associated with RDS, although presence of meconium, chorioamnionitis, and endometritis were all stronger risk factors with RRs >2.0.

Conclusions: In this cohort of high-risk term deliveries, maternal demographics and comorbidities were found not to be associated with increased risk for RDS, but novel risk factors for RDS after 37 weeks' gestation - chorioamnionitis and endometritis - were identified. A focus on preventing infectious comorbidities may help reduce incidence of RDS at full-term.Key PointsRDS risk factors vary by gestational age.Novel risk factors for RDS at full-term identified.Intrauterine inflammation associated with RDS at term.