Neonatal outcome in preterm deliveries before 34-week gestation - the influence of the mechanism of labor onset.

Purpose: To evaluate neonatal outcomes in preterm infants with less than 34 weeks after spontaneous labor, preterm premature rupture of membranes (PPROM) or iatrogenic delivery and to clarify whether the mechanism of labor onset is a risk factor for adverse short-term neonatal outcome. Methods: We performed a retrospective case-control study, which included 266 preterm newborns with less than 34-week gestation, between 2011 and 2015. Neonatal outcomes were compared according to the mechanism of labor onset. Our primary outcomes were neonatal death, sequelae on hospital discharge and a composite of these two variables (combined neonatal outcome). Results: Compared to spontaneous preterm labor, iatrogenic preterm newborns were at increased risk of respiratory distress syndrome (RDS) [Odds Ratio (OR) 3.05 (95%CI 1.31; 7.12)], and need of exogenous surfactant administration [OR 3.87 (95%CI 1.60; 9.35)]. PPROM was associated with higher risk of neonatal sepsis [OR 12.96 (95%CI 1.18; 142.67)]. There were no differences regarding the combined outcome for iatrogenic [OR 0.94 (95%CI 0.33; 2.71)] or PPROM [OR 1.11 (95%CI 0.35; 3.49)] groups. Conclusions: In our study, the different mechanisms of labor onset are associated with different neonatal outcomes. Iatrogenic preterm birth was associated with an increased risk of RDS and a higher need of exogenous surfactant administration than spontaneous group. The rate of neonatal sepsis was significantly higher in PPROM group along with a higher prevalence of histological chorioamnionitis.