The Effects of Kangaroo Care on Neonatal Neurobehavioral Organization, Infant Temperament and Development in Healthy Low-birth-weight Infants over the first year of life: the Nagasaki University Hospital Study

By Ogi, S., Fukada, M., Takahashi, T., Akiyama, T., Morichuchi, H., Nugent, J. K., Brazelton, T. B., Arisawa, K., Saitoh, H.

Introduction

The goal of this study was to determine whether Kangaroo Care intervention (KC) for healthy low-birth-weight infants would result in better outcomes in behavioral and developmental parameters over the course of the first year of life. Infants requiring intensive care because of prematurity or disease are placed in an isolated environment in the incubator. This isolation and separation necessarily reduces the opportunities for parents to interact with their infants, which in turn, may lead to stressful interactions between a mother and an infant. This experience may affect the development of the parent-infant relationship, the parent's ability to care for the infant, and may lead to deficits in the the infant's development.

For that reason, we introduced Kangaroo Care (KC) as an intervention at the University of Nagasaki University Hospital in order to reduce the separation between parents and their infants, and to promote the early parent-infant attachment and thereby promote the infant's mental and motor development. Kangaroo Care (KC) has been shown to be safe and beneficial for low-birthweight infants (e.g. Anderson, 1981; Sloan et al. 1994). However, the reported beneficial effects of KC on neonatal neurobehavioral development and temperament of infants were based mainly upon case studies and anecdotal observations but were not based on controlled empirical studies. This study was undertaken, therefore, to determine whether the provision of Kangaroo Care for healthy low-birth-weight infants would improve the behavioral, developmental and temperamental characteristics of these infants over the course of the first year of life.

Subjects and Methods

1. Study Design

This was a non-randomized intervention study in which the study group, consisting of infants who received Kangaroo Care, was compared with an historical control group made up of infants who did not receive Kangaroo Care.

2. Subjects

The study sample consisited of 53 healthy low-birthweight infants (between 1501-2099g) who were cared for at the NICU in the Nagasaki University Hospital. Infants were included in this study if they met all of the following criteria : 1) birth weight was in the range of 1500 to 2100 gms; 2) singleton birth; 3) born without complications, such as congenital heart disease, abnormal central nervous system manifestations, chromosomal aberrations or lung diseases; 4) no abnormal findings in the neurological or developmental examinations or in the neuroimaging examinations conducted after 6 months; and 5) infants' parents lived in Nagasaki city or its vicinities. Infants born to single or teenage mothers were not included in the study sample. Infants whose mothers were on welfare or who had a problematic standard of living were also excluded from the study.

A total of 75 infants were hospitalized in the NICU during 1997-1998 period following introduction of Kangaroo Care as an integral part of our nursery routine. ThirtyÐfive infants met the aforementioned sampling requirements. Nine of these infants had to be excluded because follow-up data were unavailable. The remaining 26 infants (74.3%) made up the complete KC study group. Of the 117 infants hospitalized in the NICU at Nagasaki University Hospital between 1993 and 1995, before Kangaroo Care was introduced, forty-one infants met the study sampling requirements. Of these, twenty-seven infants (65.9%), were available for follow-up studies and served as the control group, consisting of infants who did not receive Kangaroo Care.

3. Kangaroo Care Intervention Method

The NICU at Nagasaki University Hospital has 10 beds and approximately 40 to 50 low-birth-weight infants are admitted yearly; most (95-98%) of whom are born in-house. Kangaroo Care was introduced into our institution in December 1996. KC was initiated within a median of postnatal age of 1 day (range 1 to 3 days) and continued daily for all infants in the KC study group. As soon as they could tolerate handling outside the incubator, each infant was placed on the mother's (or father's) chest, in an upright position with direct skin-to-skin contact,(see figure). Simultaneously the mother was instructed to breast-feed, if the infant's condition permitted oral intake. Trained neonatologists carefully monitored the infant's physiological condition (such as respiratory and circulatory systems and body temperature) during every KC procedure. NICU nurses gave advice to the parents about the way to hold the infant on the mother's (or father's) chest, the procedure of breast feeding and how to recognize and respond to the infant's behavioral cues, (see figure). The initial KC sessions typically lasted 20-30 minutes, and were later extended to 1-2 hours, depending upon the infant's physiological-behavioral conditions. The NICU environment was manipulated by dimming the lights and playing soft music, so that the family could relax during Kangaroo Care. The visiting hours were set twice a day between 13:00 and 15:00 and between 18:00 and 19:00.

The mothers in the KC group visited the infants almost every day to perform KC, while infants in the control group received conventional medical nursing care without KC. Their management was almost exclusively conducted in incubators for approximately 2-3 weeks until the physiological functions became stable.

4. Outcome measures

The KC group and the control group were assessed on the Neonatal Behavioral Assessment Scale (NBAS) at 40 weeks postmenstrual age. Infants were assessed on the Bayley Scales of infant development , Carey's infant temperament questionnaire (ITQ) and Caldwell's home observation for measurement of the environment (HOME) at 6 months and again 12 months corrected age. The NBAS was administered by two certified NBAS examiners. The 28 behavioral items were reduced to six clusters developed by Lester et al. (1982): 1) Habituation; 2) Orientation; 3) Motor performance; 4) state range; 5) state regulation; 6) autonomic stability. The supplementary items were also scored. Mean scores were calculated for each cluster, and higher score indicates higher infant behavioral capacity.

At 6 and 12 months corrected age, each infant was assessed at home on the Bayley Scales (Bayley, 1969), the Infant Temperament Questionnaire (Carey and McDevitt, 1978), and the HOME scales (Caldwell and Bradley). The Bayley Scale was administered to determine mental and psychomotor developmental indices. Mothers were also asked to fill out the Infant Behavioral Questionnaire at this time.. The ITQ assesses temperamant on 9 categories and a mean score is calculated for each category: activity, rhythmicity, approach, adaptability, intensity, mood, persistence, distractibility, and threshold. The HOME scale was filled out in the context of a home visit and includes the following 5 categories: the mother's attitude toward the home visitors, avoidance of restriction and punishment, organization of environment, mental involvement with her child, and opportunities for variety in daily stimulation. A mean score is calculated for each category.

5. Statistical Analysis

First, X-square analysis, t-tests and Mann-Whitney U-tests were used to assess the differences between the KC and control group in terms of maternal age, parity, gestational age, birth weight, gender, Apgar scores, caesarian-section rate, duration of hospital stay.

Next, the NBAS scores, mental and psychomotor development indices in the Bayley Scale, ITQ scores and HOME score results were compared, using univariate analysis (t-test, Mann-Whitney U-test, or X2-test). Multiple analysis of covariance (ANCOVA) was conducted for a comparison of the two groups, adjusting for confounding factors. Sex, gestational age, birth weight, Apgar score at 1 minute, infants appropriate for dates (AFD infants) or infants light for dates (LFD infants), and primipara or multipara were chosen as covariants. The statistical software SPSS (version 10.0J) was used for statistical analysis .

Results

1. Background comparisons

No differences between the groups were observed in the background variables , including infant variables such as gestational age, birth weight, mode of delivery, Apgar scores and gender and maternal factors such as parity, maternal age and length of hospital stay.

2. Results of the NBAS Cluster Scores

Both the univariate analysis and ANCOVA yielded similar significant differences between the two groups on the NBAS clusters. ANCOVA showed that infants in the Kangaroo Care group had scores which were significantly higher on the Orientation (p<.02) and State Regulation (p.<.01) clusters and on the Supplementary item scores (p<..02) than the control group scores. Comparisons of individual items on the NBAS, yielded significant differences between the KC group and the control group on the Animate Visual Orientation item, the Auditory and Visual-Auditory Orientation items and on the Alertness, Cuddliness, Self-quieting, Cost of attention, General Irritability, and State Regulation items. (p<.05).

3.Results on the Bayley Scales at 6 and 12 months

T-tests and ANCOVA at 6 months corrected age, revealed no differences between KC and controls on the Bayley Scales, on either the MDI or PDI scales . However, at 12 months corrected age, there were significant differences between groups on the MDI and the PDI The KC group infants scored higher on the MDI at this time (p<.03) , while results on the PDI revealed a trend towards significance (p<.06).

4.Results of the ITQ and HOME comparison at 6 and 12 months corrected age

The results of ITQ showed significant differences between KC and control group infants on two of the temperament characteristics at 6 months but no differences were found at 12 months. Mothers in the KC group rated their infants more positively on the "mood" and "intensity" categories of the ITQ at 6 months. The results of HOME showed no differences on any of the five categories at both 6 and 12 months corrected age.

Discussion

The findings in this study suggest that Kangaroo Care in the NICU promotes the positive development of low birthweight infants over the first year of life. In the neonatal period, scores on the NBAS showed that the Orientation, State Regulation and Supplemental items clusters were significantly higher in the KC group than in the control group. In other words, when observed at 40 weeks corrected age, the infants who received Kangaroo Care were more alert and responsive, compared to infants who had not received Kangaroo Care and were less irritable and less fussy. Infants who received Kangaroo Care showed (1) a higher capability for concentrating their attention-orientation responses on animate visual-auditory stimuli and in maintaining an alert state control; (2) a higher capacity for maintaining a stability in state organization in the face of increasing levels of stimulation; (3) higher capability for state-regulation, in the ability to move from from crying or high activity state to lower states; (4) less stressful reactions in the autonomic, state regulatory and motor system; and (5) better overall organization of the neurobehavioral system. This behavioral repertoire is highly valued in Japanese culture. It is likely therefore, that the behavioral characteristics in the KC group had a modifying influence on the interactions between the infants and their parents, resulting in the promotion of positive infant-parent interactions.

Results from the Bayley Scales conducted at 12 months corrected age, showed that both the mental and psychomotor developmental indices were significantly higher in the KC group than in the control group. This suggests that that Kangaroo Care has positive effects on mental and psychomotor development that extended over the first year of life. In addition, mothers ratings of temperament showed that at 6 months, infants in the KC group were judged to be more calm and easier to care for than infants in the control group. This combined evidence suggests to us that short-term changes in parental attitude and behavior in response to the Kangaroo Care in the newborn period can serve to initiate or launch a positive cycle of interaction between parents and infants that may have long-term, albeit indirect, consequences. We can conclude that although there may not be persistent direct effects as a result of Kangaroo Care-based interventions, long-term effects may derive from indirect transactional effects (Nugent and Brazelton, 2000).

Several factors may explain why Kangaroo Care may be effective in promoting the organization of neonatal neurobehavior in the low-birth-weight infants and why it may influence mothers' perceptions of their infants' temperaments.. First, early contact between the mother and the infant may alleviate the infant's physiological and psychological stress. Second, comforting behaviors (parents holding, touching, talking, gently rocking, the smell and warmth of the parent's body etc.) tend to stabilize the infant's basic behavior and may lead to the infant's capacity for state regulation. Third, the Kangaroo Care protocol supports individualised interactions between parents and their infants. Such interactions help the parent develop sensitivity and responsiveness to the infant's behavioral signs, especially during feeding. In addition, interactions between the parents and their infants are likely to facilitate the infant's development and the parents' own recovery and stability, by reducing parental anxiety and and thereby fostering the Ôkizuna (bonding)' between the parents and the infant. Lastly, breast-feeding after birth stimulates the mother-infant bond and promotes responsive interactions between mother and baby.

(For references and further information please contact the first author at ohgi@net2.nagasaki-u.ac.jp)