Early functional closure of the ductus arteriosus associated with decreased severity of respiratory distress syndrome in preterm infants.

It has been shown that a patent ductus arteriosus may complicate the course of the respiratory distress syndrome (RDS) in preterm infants. In this study, an attempt is made to answer the question: Is there any relationship between RDS and patency of the ductus arteriosus in preterm infants, that is, do preterm infants without the RDS have early functional closure of the ductus arteriosus? Clinical observations were made on 144 preterm infants 25 to 34 weeks' gestation. Infants were included in the study if the status of the ductus arteriosus (open or closed) could be established either by clinical examination or retrograde aortography. The ductus arteriosus was closed in 59 infants within 48 hours of birth and open in 85. None of the infants with a closed ductus had severe RDS and only three had mild RDS. In contrast, 50% (43 of 85) of infants with open ductus had severe RDS. These findings suggest that early functional closure of the ductus can occur even in very immature infants, and this early closure appears to be associated with a decreased incidence of RDS.