Kangaroo Mother Care and the Bonding Hypothesis

Réjean Tessier*, Marta Cristo, Stella Velez, Marta Girón, SW; Zita Figueroa de Calume,
Juan G. Ruiz-Paláez, Yves Charpak, and Nathalie Charpak

From the *School of Psychology, Laval University, Québec, Canada; ISS-World Lab, Kangaroo Mother Care Program, Clinica del Nino, Santa Fe de Bogotá, Colombia; Clinical Epidemiology Unit, Faculty of Medicine, Javeriana University, Santa Fe de Bogotá, Colombia; and EVAL (Institut pour l'Évaluation dans le domaine Médical, Médico-social et de Santé Publique), Paris, France.

METHOD

Population and Sample • KMC and TC Interventions • Outcome Variables • Control Variables • References •

Population and Sample

This study is part of a randomized, controlled trial conducted in Bogotá, Colombia,³ involving 1084 infants that weighed <2001 grams and who were born between September 1993 and September 1994 at Clinica San Pedro Claver. Of these, 746 were eligible according to the following inclusion and exclusion criteria. An infant and mother were eligible if the mother or a relative was willing to follow instructions, and if the infant had overcome all major adaptation problems to extrauterine life, had a positive weight gain, and suckled and swallowed properly. Infant-mother dyads were excluded if the infant died; had been referred to another institution; had lethal or major malformations; had sequelae arising from perinatal problems (severe hypoxic-ischemic encephalopathy, pulmonary hypertension, etc); or had been abandoned or given for adoption. Eligible mother-infant dyads were randomized according to a stratified block randomization procedure prepared in advance. Three strata were defined, based on weight at birth (<1200 g; 1200 to 1499 g; 1500 to 2000 g), and blocks of four infants (2 KMC and 2 TC control infants) were prepared using a random number table. Of the initial group of 746 infants, 153 (20.1%) were lost because of technical problems with the video sequences (same rates in both the KMC group and the TC group); 17 (2.3%) died between eligibility and 41 weeks of gestational age (the death rate was similar in both groups³); 61 (8.2%) abandoned the study; and 27 (3.6%) mothers practicing KMC did not follow instructions to carry the infant. Consequently, the study group was reduced to 488 mother-infant dyads, 246 in the KMC group and 242 in the TC group. We compared the final group of 488 dyads with the subgroup of 258 nonparticipating dyads. We found no differences in the families' sociodemographic backgrounds or in the characteristics of the pregnancy or labor. Moreover, the neonatal variables were all the same, except that infants in the nonparticipating group were slightly heavier at birth (by 56 g) (data not shown).

The two groups were randomized before seeking consent to participate, and informed consent forms were not completed by parents of infants assigned to the TC group. This procedure, proposed by Meinert and Tonascia,¹⁹ was chosen because early discharge is very appealing to parents, and it is very likely that many of the families would have asked to be assigned to the KMC group. This procedure was accepted by the ethics committee because those assigned to the control group received the usual care provided at the participant institution.

KMC and TC Interventions

KMC has three components.¹^,³ The first is the kangaroo position. Once premature infants have adapted to extrauterine life and can breastfeed, they are discharged and positioned in an upright position on the mother's chest, with direct skin-to-skin contact. It should be pointed out that the kangaroo position has the same temperature-regulating properties of the incubator. The mother and infant may then be released from the hospital regardless of the infant's actual weight or gestational age. Infants are maintained continuously in this position, 24 hours a day, until they demonstrate, behaviorally, that they are ready to leave, usually at ~37 to 38 weeks' gestational age. Other caregivers (eg, the father, grandparents, etc) may alternate with the mother as a kangaroo position provider. This first component is the related most directly to this study's psychological hypothesis.

The second component is kangaroo nutrition. Although breastfeeding is the prime source of nutrition, infants also may receive preterm formula and vitamin supplements when necessary. The third component is the clinical control: infants are monitored on a regular basis daily until a weight gain of at least 20 g per day is observed. Afterward, weekly visits are scheduled until term (40 weeks' gestational age), which constitutes the ambulatory minimal neonatal care.

In the TC group, infants are kept in incubators until they can regulate their temperature and are thriving (ie, have an appropriate weight gain). They are discharged in accordance to current hospital practice, that is, usually not before their weight is ~1700 g. This period is when infants no longer need intensive care, and stay in hospital is the only difference between them and infants in the KMC group. Otherwise, as with those in the KMC group, mothers are encouraged to visit and breastfeed their infant as early as possible during the inpatient period, and infants receive preterm formula and vitamin supplements when necessary. These infants received the same outpatient care and follow-up as infants in the KMC group. Therefore, the TC intervention includes an inpatient period (from eligibility to discharge) as well as an at-home period lasting until term.

Outcome Variables

The Mother's Perception of Premature Birth Questionnaire

Essentially, this questionnaire addresses three aspects of the mother's life linked to experiencing a premature birth. It has been designed based on interviews with the mothers and takes into account published empirical research on the experience of prematurity. From a theoretical aspect, the questionnaire includes three general domains: 1) the mother's social, family, and institutional environment -- and in particular, her perception of the respective support received from these three environments; 2) the mother's feelings and worries about her LBW infant (anxiety, guilt); and 3) the mother's sense of competence and confidence in her ability to nurture her premature infant. These three domains are measured using a Likert scale (1 to 5), 24 hours after birth and when the infant has reached 41 weeks' gestational age. Although the questions varied somewhat in the 24-hour and 41-week questionnaires (in terms of the contextual difference), the factor analyses conducted on the sample of 488 families suggested the presence of the same three score model at each time point: mother's sense of competence, perception of social support, and feeling of stress and worry. These factor scores are used in this study.

The Nursing Child Assessment Feeding Scale

This scale measures the emotional bond between mother and child, and consists of 76 binary items organized according to six conceptual subscales. Four of them describe the mother's behavior toward her infant: sensitivity to the infant, response to infant's distress, and behaviors related to socioemotional, and cognitive stimulation of the infant. The remaining two subscales describe the infant's response to the mother (clarity of cues, responsiveness). The validity and reliability of the scale are well established,²⁰ and interrater agreement is 0.85 in this study.

Control Variables

Many control variables have been introduced to optimize data interpretation. They include gestational age at birth, gender, weight, height and head circumference at birth; intrauterine growth diagnosis according to the Lubchenco classification; parity; Apgar score at 1 and 5 minutes; diagnoses at eligibility time; age, weight, height, and head circumference at eligibility; family sociodemographic descriptors; and pregnancy and delivery variables.

Procedures

All infants were evaluated at birth, at time of eligibility, and at term by a team of pediatricians, nurses, social workers, and psychologists. All mothers (1084) participated in a structured interview after 24 hours in the hospital and after their respective infants reached a gestational age of 41 weeks, for the dyads remaining in the study. A 15-minute interaction-feeding sequence was videotaped in a small room near the clinic when the parent and child attended the follow-up clinic at gestational age 41 weeks. These sequences were scored according to the Nursing Child Assessment Feeding Scale. Performing the entire study under completely blind conditions was not possible because during the LBW follow-up clinic, the psychologists involved with the patients also were both observers during the videotaping as well as final evaluators. However, the large number of subjects, the 1-year interval before videotaping, and the coding procedure ensure that the study was performed under quasiblind conditions.

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