The relation between neonatal heart period patterns and developmental outcome.

Developmental psychophysiologists have long been interested in a means for evaluating infants at risk for cognitive disabilities. The current research addressed the utility of a noninvasive measure of cardiac vagal tone in predicting developmental outcome. At 40 weeks conceptional age, 3 min of resting EKG were recorded from 80 infants. Four groups of infants were evaluated: prematures who had no medical complications in the postnatal period; prematures who experienced respiratory distress syndrome during the postnatal period; term infants who experienced birth asphyxia during labor and/or postdelivery; and healthy term infants. The mental scale of the Bayley Scales of Mental Development was administered at 8 and 12 months conceptional age. Heart period data were analyzed to derive mean heart period, heart period variability, and estimates of vagal tone for each subject. Analyses of the relationship between the heart period variables and 8- and 12-month outcome (i.e., Bayley Scales) indicated that infants with high vagal tone at 40 weeks conceptional age always had positive developmental outcome at both eight and 12 months of age. Infants with low vagal tone had varied outcomes. Measures of medical complications and other measures of heart period variability were not related to developmental outcome. The results suggest that measurement of cardiac vagal tone may provide an important means for assessing risk in birth stressed populations.