This study examined infant response and recovery from a social challenge and parent responses. Behavioral and physiological responses were measured from forty-three 5- and 6-month-olds infants during a modified still-face procedure that used an additional still-face reunion sequence. Results confirm the hypothesis that infants of more responsive parents show more regulation than infants of less responsive parents. Infants of more responsive parents showed greater regulation of heart rate and negative affect during the final episode of the procedure than infants of less responsive parents. In addition, this procedure elicited a cortisol response (from .22 microg/dl to .31 microg/dl). Findings suggest important links between parent behavior and infant stress reactivity and regulation.

Data from animal models indicate that neonatal stress or pain can permanently alter subsequent behavioral and/or physiological reactivity to stressors. However, cumulative effects of pain related to acute procedures in the neonatal intensive care unit (NICU) on later stress and/or pain reactivity has received limited attention. The objective of this study is to examine relationships between prior neonatal pain exposure (number of skin breaking procedures), and subsequent stress and pain reactivity in preterm infants in the NICU. Eighty-seven preterm infants were studied at 32 (±1 weeks) postconceptional age (PCA). Infants who received analgesia or sedation in the 72 h prior to each study, or any postnatal dexamethasone, were excluded. Outcomes were infant responses to two different stressors studied on separate days in a repeated measures randomized crossover design: (1) plasma cortisol to stress of a fixed series of nursing procedures; (2) behavioral (Neonatal Facial Coding System; NFCS) and cardiac reactivity to pain of blood collection. Among infants born ≤ 28 weeks gestational age (GA), but not 29-32 weeks GA, higher cumulative neonatal procedural pain exposure was related to lower cortisol response to stress and to lower facial (but not autonomic) reactivity to pain, at 32 weeks PCA, independent of early illness severity and morphine exposure since birth. Repeated neonatal procedural pain exposure among neurodevelopmentally immature preterm infants was associated with down-regulation of the hypothalamic-pituitary-adrenal axis, which was not counteracted with morphine. Differential effects of early pain on development of behavioral, physiologic and hormonal systems warrant further investigation.

Objective-Little is known about the developmental trajectory of cortisol levels in preterm infants after hospital discharge.Study design-In a cohort of 225 infants (gestational age at birth <33 weeks) basal salivary cortisol levels were compared in infants born at extremely low gestational age (ELGA, 23-28 weeks), very low gestational age (VLGA, 29-32 weeks) and full-term (37-42 weeks), at 3, 6, 8 and 18 months corrected age (CA). Infants with major neurosensory and/or motor impairment were excluded.Results-At 3 months CA, salivary cortisol levels were lower in both preterm groups compared to the full-term infants (p = .003). Conversely, at 8 and 18 months CA, the ELGA infants had significantly higher basal cortisol levels than the VLGA and full-term infants (p = .016; p = .006 respectively).Conclusions-In ELGA infants, the shift from low basal cortisol levels at 3 months to significantly high levels at 8 and 18 months CA suggests long-term 're-setting' of endocrine stress systems. Multiple factors may contribute to these higher cortisol levels in the ELGA infants, including physiological immaturity at birth, cumulative stress related to multiple procedures and mechanical ventilation during lengthy hospitalization. Prolonged elevation of the cortisol "set-point" may have negative implications for neurodevelopment and later health. Publisher's Disclaimer: This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.No author has any potential conflict of interest with this manuscript. Early environmental stress can permanently reorganize hormonal, physiological and behavioral systems, and increase vulnerability to illness and disorders later in life, a process referred to as "early programming." 1-6 For example, in rats, early adverse experiences such as prenatal stress, maternal separation or early deprivation result in increased stress hormone responses throughout the preweaning period and into adulthood. 2,3,6 Increased exposure to endogenous corticosteroids has adverse effects on cognitive abilities 7 and increases emotionality and anxiety-like behaviors in aversive situations. 8,9 NIH Public AccessIn general, sicker and smaller infants often show relatively low cortisol levels while in the neonatal intensive care unit (NICU). 10 We have recently shown a developmental shift whereby greater cumulative neonatal stress (higher number of skin-breaking procedures from birth to term) predicted lower cortisol levels in the NICU, 11 but elevated cortisol levels at 8 months corrected age (CA). 12 Little is known about the developmental trajectories of cortisol secretion in preterm infants after hospital dis...