Developmental changes in the responses of preterm infants to a painful stressor

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Abstract

The purpose of this investigation was to examine longitudinally gestational age and developmental differences in preterm infants’ self-regulatory abilities in response to a painful stressor, as well as associations between behavioral and cardiovascular responses. Participants included 49 healthy premature infants. Behavioral and cardiovascular responses to a heel stick blood draw were compared between infants of 28–31 and 32–34 weeks’ gestation age at birth. Both gestational age groups displayed behavioral and cardiovascular indications of stress in response to the blood draw. However, both shortly after birth and several weeks later, infants born at younger gestational ages (28–31 weeks) were more physiologically reactive. Evidence that the behavioral stress responses of 28–31 weeks’ gestation age group preterm infants do not reflect their physiological responses suggests that evaluation of preterm infants’ experiences and risk require assessments of both physiology and behavior. The greater stress vulnerability of the 28–31 weeks’ gestation group relative to the 32–34 weeks’ gestation group and the implications of this for subsequent development are discussed.

Section snippets

Participants

Participants included 49 healthy premature infants; 21 were of a younger GAB (YGAB), born between 28 and 31 weeks’ gestation (M = 29.81; SD = .98; 9 girls, 12 boys) and 28 were of an older GAB (OGAB), born between 32 and 34 weeks’ gestation (M = 33.11; SD = .69; 15 girls, 13 boys). Participants were recruited from two large metropolitan hospitals with NICUs: University of Minnesota Children's Hospital-Fairview University Medical Center and Hennepin County Medical Center, with 670 and 250 admissions per

Baseline levels

As expected, the baseline heart rate of the YGABt1 infants was significantly higher than the heart rate of the OGAB preterms [t(47) = 2.11, p = .04; see Table 1]. In addition, the baseline heart rate levels of the YGABt2 infants remained significantly higher than the heart rate levels of the OGAB infants [F(1,40) = 12.74, p = .001] and were not significantly different from their own baseline heart rate levels at time one [F(1,33) = 2.91, p = .10].

Responses to the heel stick blood draw

Controlling for baseline heart rate levels (as well as the

Discussion

The first goal of the present investigation was to longitudinally examine developmental differences in preterm infants’ ability to self-regulate in response to stressors to gain a better understanding of the vulnerability of preterm infants to stress exposure. The second goal was to integrate assessments of both physiology and behavior to examine whether behavioral responses reflect physiological responses, and whether the association between behavioral and physiological responses differs by

Acknowledgements

This research was supported by a grant from the Minnesota Medical Foundation (643-7051) to the last author and a K05 award (MH66208) to the third author. The authors wish to give a very special thank you to the families who participated in this research and to the nurses, lab technicians, and physicians at the Fairview University Medical Center and Hennepin County Medical Center, Minneapolis, MN. Thanks also to the undergraduates at the University of Minnesota who assisted with data collection

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