Risk Factors for Acute Respiratory Morbidity in Moderately Preterm Infants

Background Infants born preterm account for a substantial part of neonatal morbidity, with acute respiratory disorders being a dominating clinical problem. Whereas focus in recent studies has been on extremely and very preterm infants, less is known about contemporary rates and risk factors for acute respiratory morbidity in moderately and late preterm infants. The objective of this population-based Swedish study was to establish rates for different acute respiratory diseases in moderately preterm infants, and to identify maternal, obstetric and neonatal risk factors for the two most common diagnoses, transient tachypnoea of the newborn (TTN) and respiratory distress syndrome (RDS). Methods The study included 4679 moderately preterm [gestational age (GA): 30 to 34 weeks], 15036 late preterm infants (GA 35 to 36 weeks) and 451479 term infants (GA: 37 to 41 weeks). All infants were born in 20042008. Results In moderately preterm infants, risk factors for TTN in multivariable analyses were multiparity, caesarean section before and after onset of labour, male sex, Apgar score 46 at 5min and lower GA. Risk factors for RDS were multiparity, caesarean section before and after onset of labour, male sex, Apgar score <7 at 5min and lower GA. Preterm rupture of membranes, antenatal corticosteroid treatment and being small for gestational age reduced the risk of RDS. Conclusion We conclude that acute respiratory morbidity in moderately preterm infants is common and predicted by multiparity, caesarean section, low Apgar score and male sex.