Oxytocin trajectories and social engagement in extremely premature infants during NICU hospitalization.

Extremely premature infants, born 28 weeks gestation or less, are at high risk for impaired socioemotional development, due in part to exposure to early stressful social experiences that alter brain development. Understanding mediators that link experience with outcomes is necessary to assess premature infant responses to social experiences that are critical to brain development. The hormone oxytocin (OT), released during supportive interactions, has potential as a biomarker of the premature infant's responses to social experiences. The purpose of this study was to examine associations among infant plasma OT trajectories and maternal-infant social engagement behaviors during initial hospitalization. This study also examined demographic correlates of engagement behaviors in mothers and infants. Plasma from 28 extremely premature infants, born gestational ages 25-28 6/7 weeks, was collected at 14 days of life, then weekly until 34 weeks. Social engagement behaviors were measured by the Parent-Child Early Relational Assessment during a videotaped feeding when the infant was receiving one-quarter full oral feeds. Maternal-infant demographics were extracted from the medical record. Higher infant plasma OT was associated with lower infant social engagement, but no associations were found with maternal social engagement. Infant social engagement was positively related to maternal social engagement. Maternal parity was related to maternal social engagement, and infant demographics did not predict infant social engagement. The significant, yet negative, association between infant OT and engagement provides support for the measurement of OT as a neurobiological antecedent to infant social behaviors. Finally, this research suggests that during the earliest period of infant socio-behavioral development, premature infants are behaviorally reactive to the social engagement behaviors of their mothers.