Effect of holding on co-regulation in preterm infants: a randomized controlled trial

To determine whether kangaroo holding of healthy preterm infants over the first eight weeks of an infant's life facilitates co-regulation of salivary cortisol between mother and infant.

Randomized control trial. Infants were assigned to receive 1h of daily kangaroo (skin-to-skin contact on the chest of mother) or blanket holding (dressed and held in mother's arms). A registered nurse visited mothers weekly for eight weeks to encourage holding and provide information about infant development. A control group had no holding restrictions and received weekly brief social visits.

The study included 79 preterm infants, born between 32 and 35weeks gestational age and were a mean of 15days (±5.7) at enrollment.

Co-regulation was conceptualized as progressive reduction in the absolute difference between mother and infant cortisol levels across 60min of holding at each holding session. Mother and infant cortisol levels were measured before holding and at 30 and 60min after holding began during three holding sessions (baseline and at two and eight weeks after study initiation). Primary analyses were conducted using hierarchical linear models.

There was much variability in cortisol levels. Levels of mother and infant cortisol decreased during holding. No significant co-regulation occurred in any group at any holding session or over time.

Decreasing level of cortisol in both mothers and infants suggests that holding promoted the expected decline in stress hormone levels. However, supported holding methods did not differentially affect co-regulation compared to controls. Holding is pleasurable and stress may need to be present in order for mothers and infants to demonstrate co-regulation in cortisol levels.