Developmental psychobiology

Kangaroo care (KC), has been shown to promote healthy development for both
pre-term and full-term infants, and to improve mother-infant bonding (Ludington-Hoe,
2011; Charpak et al., 2005). Current research on the maternal benefits of kangaroo care is
scarce, primarily focuses on early KC, and is mostly qualitative in nature (Fegran,
Helseth, & Fagermoan, 2008; Matos et al., 2010). The present study examined the effect
of late KC on maternal behaviors, sensitivity, and mother-infant interactive mutuality
when infants were 3 months of age. Mothers who used kangaroo care as directed were
found to have greater bonding scores and less anxiety about caring for their infants as
measured through the Postpartum Bonding Questionnaire. Kangaroo care was also found
to have an effect on mothers’ ability to effectively calm their infants after an arm restraint
task. Further research on the usefulness of late intermittent KC with full-term infants is
needed.

The current study examined the effects of kangaroo care on breastfeeding
practices, infant stress reactivity, and biobehavioral measures of mother-infant bonding
across the first 3 months postpartum. Additionally, the role of breastfeeding in infant
cortical maturation in the frontal lobe was examined. Thirty two mother-infant dyads
participated in the current study; 16 mother-infant dyads were randomly assigned to the
kangaroo care group and 17 mother-infant dyads were assigned to the control group.
Mothers in the kangaroo care group received training on proper kangaroo care procedures
by a trained administrator during the first 1-2 weeks postpartum. Mothers in the kangaroo
care group were asked to use the kangaroo care procedure for 1 hour per day for 6 weeks. Maternal perceptions of fetal attachment, mood, feeding intentions, and urinary
oxytocin measurements were assessed prenatally. At a newborn visit, infant
neurobehavioral functioning and urinary oxytocin measurements were assessed. Maternal
mood and feeding practices were also assessed at the newborn visit. At 3 months
postpartum, mother-infant dyads were assessed on urinary oxytocin measurements.
Mother-infant dyads were recorded during a play session and feeding session. Infant
baseline EEG recordings were taken over a 5 minute period. Infant cortisol
measurements were collected from infant saliva before and after a mild behavioral
stressor, an infant arm restraint procedure. Maternal perceptions of postpartum bonding,
mood, infant temperament, and feeding practices were also assessed. Results indicate that
kangaroo care produced medium to large effects on cortisol reactivity, dyadic bonding,
and breastfeeding practices if kangaroo care was practiced for the recommended amount
of time. Kangaroo care produced medium to large effects on oxytocin levels in motherinfant
dyads regardless of use. Cortical measures of infant frontal activity indicated that
all infants in the samples displayed functional maturity of the frontal lobe. Kangaroo care
can be used a viable, low-cost tactile procedure that can be implemented after birth to aid
in breastfeeding practices, mother-infant bonding, and lower infant stress reactivity.
Infants in the study who received at least one breastfeeding session displayed advanced
patterns of frontal activation. Further study is needed to determine if peripheral oxytocin
measurements are 1) reliable and 2) are indicative of dyadic bonding behaviors.

This study examined the hypothesis that cognitive immaturity may serve an adaptive purpose for children at a time in ontogeny when they are not capable of ensuring their own survival. Participants were presented pairs of scenarios of 3- and 9-year-old children expressing either immature or mature cognition. Participants were asked to select the child (immature vs. mature) which best reflected each of 11 different psychological traits that were ultimately grouped into 3 trait dimensions: cute, deceptive, and smart. Participants received one of 6 pairs of scenarios reflecting examples of either intuitive cognition or nonintuitive cognition. Participants selected the immature child as being more cute and less deceptive than the mature child for the intuitive vignettes, but not for the nonintuitive vignettes. This pattern suggests that some forms of immature cognition do indeed bias adults to feel more favorably toward the children who express them and may foster positive parent-child relationship.

Maternal neuroendocrine function during pregnancy has been related to a number of pregnancy outcomes including less optimal fetal growth patterns. Animal models have consistently demonstrated that glucocorticoid infusions to the mother result in fetal growth restriction and norepinephrine infusions in reduced blood flow to the fetus. Similarly, human studies reveal that elevated maternal HPA axis and adrenal function (associated with stress anxiety and depression) during pregnancy is related to prematurity and low birthweight. The present study examined the relationship between maternal cortisol and norepinephrine and fetal growth measures during mid-gestation. Correlation analyses revealed that both maternal psychological (daily hassles, depression and anxiety) and biochemical (cortisol and norepinephrine) variables were negatively related to fetal growth measures. Hierarchical multiple regression analyses further revealed that maternal cortisol was the best single maternal predictor of fetal growth accounting for a significant portion of the variance even after controlling for gestational age and fetal gender. Results from the structural equation model indicate that the effects of maternal psychological distress on fetal growth are mediated by maternal cortisol. Potential mechanisms of action are discussed.