CLINICAL DEFENSE RESPONSE TO COLD AND NOISE IN PRETERM NEONATES AFTERINTRAUTERINE CONDITIONS ASSOCIATED WITH CHRONIC STRESS

Threatening stimuli may trigger abnormal reaction patterns in animals and infants. We investigated whether chronic intrauterine stress influ enced these reactions. The autonomic defense response to cold and nois e in 21 preterm newborns who had suffered from chronic intrauterine st ress, such as maternal smoking, maternal hypertension, and intrauterin e growth retardation (STR-group) was compared with the response in 30 preterm newborns without such condition (C-group). An ice cube was app lied to the forehead and a 90 dB bleeptone was presented to the ears. After the cold test the heart rate, systolic, diastolic, and mean bloo d pressure increased in both groups, but to a lesser extent in the STR -group: the heart rate increased more at 2 minutes in the C-group (p=0 .009), and the systolic blood pressure was higher in the C-group at 30 seconds (p=0.007). The respiratory rate decreased in both groups. Aft er the auditory stimulus, no significant difference in response betwee n the two groups was seen for any of the parameters. The number of aro usals between the two groups was similar for both tests; they uniforml y resulted in increased heart and respiratory rates. The classic passi ve defense response was not observed in either group of preterm newbor ns. The observed reaction could be defined as a combination of a sympa thetic, active fight-or-flight reaction and a parasympathetic passive freezing, or paralysis, reaction. The latter was less pronounced in th e C-group. This may point to a change in the maturation of the autonom ic nervous system after chronic intrauterine stress. It is speculated that this could make these infants more vulnerable in stressful situat ions.