Maturation of autonomic control in preterm infants.

In order to investigate the development of autonomic control and its relation to postnatal illness, healthy term, healthy preterm, and preterm infants who had recovered from respiratory distress syndrome (RDS) were seen around the expected date of their birth, 40 weeks conceptional age (C.A.), and again at 3 months conceptional age. Three minutes of resting EKG were collected at each age point while the infant was in a quiet, alert state. Measures of resting heart period and heart period variability were derived. Results revealed the influence of maturity and illness on autonomic activity. RDS and healthy preterm infants, at 40 weeks C.A. exhibited a pattern of small heart period compared to healthy term. RDS preterm infants at 40 weeks C.A. exhibited less overall variability than either healthy group and across age displayed less short-term variability than the healthy infants. The data suggest that autonomic activity during the early months of life may be affected by both prematurity and postnatal illness. The significance of these data in understanding term/preterm differences in the neonatal period is discussed.