Introduction

Mothers hold babies to their chest instinctively. Currently, in less well developed societies, where cribs, strollers, and infant seats are not common, mothers or other caregivers carry their infants on their chest for many hours a day.¹ Often there is nothing between the caregiver’s chest and the baby’s skin other than a diaper. This paradigm of holding an infant with ventral skin-to-skin contact (SSC), typically in an upright position and with the swaddled infant on the chest of the parent, is also commonly referred to as kangaroo care (KC), due to its simulation of marsupial care. While there are no recordings of infant care from the distant past, it is likely that KC of newborns has been practiced for eons. Paradigm of Kangaroo Care in the Preterm Neonate Essay. An example of the basic survival value of skin-to skin contact between infant and mother can be demonstrated when there is no interference from health care providers at delivery, specifically when the infant is placed skin-to-skin on its mothers chest at birth, within 20 minutes it will work its way toward the nipple and suckle.²

The medical use of this natural phenomenon was originally introduced by Edgar Rey Sanabria in Columbia in 1978 as a strategy to replace the function of incubators, which were in short supply in that country. Infants who were preterm, but otherwise stable, were put in continuous KC with their mothers. There are variations in KC practices, but all of it involves SSC. For example, kangaroo mother care (KMC) refers to SSC that is provided continuously until the infant begins to sweat and resist the position, an indication of more mature temperature regulation and development. Breastfeeding is exclusive, and discharge home occurs earlier than usual, when the baby is stable and the mother is comfortable providing continuous SSC.^3–5 Fathers and other family members can also be providers when the mother is unavailable.⁶

In resource-rich countries, SSC is seen as complementary to incubator care, and so continuous KC is rare. Implementation of SSC in hospitals has largely been motivated by a desire to humanize what has become a medical experience, and as partial fulfillment of the requirements set out in the Baby Friendly Hospital Initiative (BFHI).⁷ The purpose of SSC in resource-rich countries has therefore been focused on facilitating infant transition to extrauterine life, promoting early bonding and establishing exclusive breastfeeding. SSC has shown added benefit for the mother, including reduced incidence of post-partum hemorrhage;⁸ however, this review focuses primarily on the benefits to infants. More recently, strong evidence related to the pain-relieving benefits of SSC, almost exclusively studied in developed countries, has emerged.

KC has been studied for its effect on mortality, morbidity, physiological stability, breastfeeding, parental bonding, development, and pain control.^9–11 Yet despite consistent positive findings for all outcomes, adoption of KC as a routine clinical practice remains extremely variable across settings. It is recommended that KC is a feasible, natural, and cost-effective intervention, and should be standard of care in the delivery of quality health care for all infants, regardless of geographic location or economic status. What remains uncertain is whether continuous KC should be recommended in all settings or if there is a critical period of initiation, dose, or duration that is optimal. This review provides a synthesis of our current knowledge about the benefits of KC, highlighting differences and similarities across gestational age, low and higher resource countries, and in a non-pain and pain context. Additionally, implementation considerations and unanswered questions for future research are addressed. Paradigm of Kangaroo Care in the Preterm Neonate Essay.

Benefits of KC

Since the inception of KC as a low-cost alternative to incubator care in areas with limited resources, clinicians and researchers have, over time, documented both physiologic and behavioral benefits for infant and mother (see Table 1). Many of these benefits have been researched sufficiently to permit meta-analysis, such that two Cochrane reviews exist on the subject.^9,10 One focuses on healthy term or late-preterm newborns,⁹ while the second includes low birth weight infants.¹⁰

Table 1 Benefits of KC in non-pain context Notes: aStability of the Cardio-Respiratory system In Premature infants. Composite tool that indicates physiologic stability; bHome Observation for Measurement of the Environment,assesses quality and extent of stimulation available to a child in the home environment. Abbreviations: LBW, low birth weight; NICU, neonatal intensive care unit; RCT, randomized controlled trial; KC, kangaroo care; MD, mean difference; V, vaginal; C/S, cesarean section; GA, gestational age; RR, relative risk; CI, confidence interval; HR, heart rate; hx, history; REM, rapid eye movement; EEG, electroencephalography; BF, breast feeding; BKC, birth kangaroo care; OR, odds ratio; N/A, not available; MEP, motor evoked potentials; PMA, postmenstrual age; SC, standard care; CG, control group; EBF, exclusive breastfeeding .

Physiologic benefits

Homeostasis (temperature regulation, physiological stability, blood glucose)

When compared with standard care (incubator, radiant warmer, or open crib), KC has shown benefits for homeostasis. Preterm infants who receive KC are more likely to maintain a healthy body temperature, and show increased cardiorespiratory stability.^10,12–20 Looking at the entire hospitalization, KC is associated with decreased likelihood of infection, severe illness, and death.^10,21 Additional evidence for the positive influence of KC exposure on autonomic regulation comes from a recent longitudinal study,²² which showed a significant increase in baseline autonomic stability at 10 years follow-up. Even a very small amount of KC (1 hour a day for 14 days) provided to preterm infants compared with infants cared for only in an incubator was associated with improved infant and maternal outcomes. These findings are of particular interest because they are the first to demonstrate the long-lasting value of early KC.

Implications for practice

The evidence for the ability of KC to promote homeostasis is strong, especially in developing countries, where good evidence suggests that continuous KC can reduce mortality.¹⁰ Unfortunately, the clinical picture is less clear in the developed world. The best evidence available is focused on intermittent use of KC, and while homeostatic benefits should theoretically persist when KC is continuous, there is a lack of studies designed to address this. Combined analysis conducted by Conde-Agudelo et al found that benefits that were clear in less developed countries (eg, reduction in sepsis, mortality, and severe illness) were not present when studies were limited to those in developed countries.¹⁰ There remain limitations in making conclusions regarding the optimal time spent in KC to achieve maximum benefits. Feldman et al²² offer compelling evidence that an average of 1 hour a day of KC may impart long-lasting benefits, but evidence is still lacking as to whether shorter or longer time periods may impart different benefits. Clinicians should use best judgment in balancing the illness acuity of individual infants, parent availability, and potential benefits.

Implications for research

Benefits that were discovered through research in developing countries should not be extrapolated to better resourced countries. There remains a paucity of studies investigating the effect of KC on mortality, infection, and serious illness in resource-rich countries. Methodologically rigorous studies are needed to understand how to maximize the clinical benefits of KC in hospital environments where advanced support is readily available. Many of the questions that remain are most appropriately answered by randomized controlled trials. In both developed and developing countries, our understanding of the physiological benefits of KC would benefit from routine use of composite physiological measures from which investigators can interpret a more meaningful clinical picture. In a review of the benefits of KC in term children, Moore suggests the use of SCRIP scores, (eag, stability of the cardiorespiratory system as the primary physiological outcome).⁹ This would help draw conclusions that more broadly address stability as opposed to attempting to interpret outcomes separately.

There is little evidence from which to determine minimum times for KC to maximize physiological benefits, which are of particular interest to clinicians in countries like Canada and the United States of America (USA) where parent availability is often limited. Continuous KC potentially represents a free alternative to expensive equipment, but the price may be high for parents who bear the burden of additional costs associated with being available in neonatal intensive care units. A recent systematic review and meta-analysis²⁸ of 29 papers addressing parental experiences during KC, including 401 mothers and 94 fathers, revealed two overarching themes, ie, a beneficial and restoring effect on both themselves and their child(ren), but also an increased burden, which was a draining experience. Improving our understanding of the optimum daily duration of KC will be important in order to ensure that we do not unjustifiably transfer burden from the health care system to parents.

Late-preterm infants, primarily delivered in developed countries, who are deemed healthy enough to remain on the post partum ward, have been excluded from much of the current literature.⁹ If physiological stability can be improved by introduction of early and sustained KC interventions for this population, there is potential for considerable impact on health care costs, family burden, and reduction of interventions. Similarly, there is a lack of analysis of benefits for infants born via cesarean section. In the studies included in this review, none considered analysis of outcomes in cesarean deliveries separately. This lack of evidence was one of the issues highlighted in a recent Cochrane review of vaginal versus cesarean birth for preterm infants.²⁹ While results of that meta-analysis found no difference in any of the reported outcomes (respiratory distress, Apgar scores, mechanical ventilation, supplemental oxygen), investigators were only able to include four trials, the most recent published in 1996.

For preterm or low birth weight infants, there is a need for more research examining the effectiveness of continuous early KC for both nonstabilized and relatively stabilized infants.¹⁰ Perhaps unstable infants would benefit differentially from KC when compared with stable infants. Paradigm of Kangaroo Care in the Preterm Neonate Essay. Moreover, it remains unclear whether physiological benefits are variable depending on the KC provider, because there is so little research comparing mothers and alternative providers, such as fathers, grandparents, or trained volunteers.²²

Growth, neurodevelopment, and neurosensory impairment

Perhaps one of the most interesting benefits of KC is the effect on sleep, neurodevelopment, and growth. A recent study by Feldman et al²² provides compelling evidence in this domain as well as in the physiological domain. They found that infants who received an average of 1 hour of KC for 14 days showed a more organized sleep–wake cycle at 10 years of age. Short-term benefits of KC on sleep patterns in preterm infants have been well established and include an increase in quiet sleep, longer cycles, and increased respiratory regularity.^15,30,31

As a consequence of the tremendous rate of neurodevelopment that occurs in utero, it is no surprise that preterm infants often suffer neurophysiological sequelae.^32,33 Two recent cohort studies used electroencephalographic complexity to measure differences in neurological maturity between preterm infants who received KC and those who did not. While sample sizes were small, the investigators were able to identify a relationship between KC and increased electroencephalographic complexity.³⁴ Additionally, the results showed an increase in primary motor cortex synchronization in response to transcranial magnetic stimulation in the group of infants that received KC.³⁵ These results suggest that KC plays a role in supporting neurodevelopment, which is consistent with earlier findings.³¹

A recent clinical trial in an Indian hospital compared sustained KC with conventional care in preterm infants. The infants were enrolled in groups of five, with the smallest three infants in each group being assigned to the KC condition.³⁶ Growth at a corrected gestational age of 40 weeks was similar between the intervention group and the control group, but infants receiving KC achieved more rapid physical growth after this point. Evidence for an association between KC and augmented growth comes from the meta-analysis by Conde-Agudelo et al, which found benefits for both continuous and intermittent KC.¹⁰ When KC was continuous (KC) it was associated with an increase in weight gain, length, and head circumference.

Clinical implications

Current evidence suggests that KC improves sleep, neurodevelopment, and growth, and should therefore be encouraged in clinical practice. While there is a lack of guidance regarding the optimal duration, the compelling outcomes described by Feldman et al were the result of just 14 days of sessions lasting an average of 1 hour.²⁰ Given the lack of uptake of any variation of KC in some practice settings, it would be reasonable to recommend that all infants should have KC initiated as soon as possible after birth and receive at least this minimal dose daily.

Research implications

The potential for KC to impact neurodevelopment and growth in preterm infants is exciting, but there is still much left to be understood. Dose-response studies would be particularly interesting because they would help families and clinicians to collaborate in order to achieve the best outcomes for the least cost. Studies should be randomized when possible in order to help control for unknown confounding variables. Paradigm of Kangaroo Care in the Preterm Neonate Essay.

Investigators should take advantage of the diverse range of instruments available to them in order to learn more about the neurodevelopment changes associated with KC. For example, is the hypothesis that KC increases the rate of neurodevelopment supported by brain imaging? Are the benefits exclusive to pathways related to attention and sleep regulation, or do preterm infants who receive KC have more rapid peripheral neurodevelopment as well?

Studies designed to elucidate the mechanisms via which KC imparts its benefits are lacking. Sleep, neurodevelopment, weight, and length are clinically relevant outcomes but we also need studies designed to tease out how KC interacts with these.

Behavioral benefits

Breastfeeding rates

The BFHI, devised by the World Health Organization, is an international set of guidelines to promote, protect, and support breastfeeding.⁷ Provision of KC is one of the “ten steps to successful breastfeeding” outlined in the BFHI. Although initially developed for healthy term infants, an international group of experts has made recommendations for adapting the “ten steps” of the BFHI to be applicable to ill and premature infants in neonatal settings.³⁷ In the modified BFHI for neonatal units proposed by Nyqvist et al,³⁷ provision of early, continuous, and prolonged KC without unjustified restrictions is cited as crucial to improving breastfeeding outcomes in this vulnerable infant population.

Evidence supports the influence of KC in increasing maternal milk volume and promoting breastfeeding exclusivity and duration in preterm infants.^38–40 Flacking et al⁴¹ used a prospective longitudinal design to examine the influence of KC on breastfeeding in two age groups: those born very preterm (less than 32 weeks’ gestational age) and preterm (32–36 weeks’ gestational age). They found that in very preterm infants, those who were breastfeeding at 1, 2, 5, and 6 months post discharge has significantly more KC time in hospital. In randomized controlled trials comparing KC interventions with standard care, preterm infants demonstrate initiation of earlier breastfeeding,¹⁰ higher breastfeeding exclusivity,^10,42 and a longer duration of breastfeeding^10,43,44 when compared with infants who are cared for in an incubator or are wrapped in blankets when held by their mothers.

Clinical implications

Based on consistent evidence for KC in promoting breastfeeding, clinicians should encourage KC for preterm infants both in the neonatal intensive care unit and following hospital discharge.^5,6 Given the variability in duration of KC provided across studies, there is no consensus regarding the length of time required to optimize the benefit for breastfeeding outcomes. Therefore, it is recommended that mothers be informed of the benefits of KC for breastfeeding, and that they are encouraged and supported in providing KC as early as possible (ideally from birth) and for as long and as often as they would like.³¹

Limitations and implications for future research

A limitation in the research examining KC and breastfeeding is the reliance on maternal self-report. Given the potential for bias in reporting breastfeeding outcomes due to the social desirability of exclusive breastfeeding, it is important to interpret the findings with caution. While some researchers⁴⁴ have considered and controlled for baseline maternal intentions to breastfeed, this is not consistently done. Given the significant influence of prenatal intentions to breastfeed in predicting long-term breastfeeding outcomes,⁴⁵ this is an important variable to measure and report in future studies. While Flacking et al⁴¹ found that KC had the greatest benefit for very preterm infants (born at less than 32 weeks’ gestational age), research in this young age group is limited. Future studies examining the relationship between KC and breastfeeding initiation, duration, and exclusivity in infants born at a gestational age of less than 32 weeks is needed. There was variability in measures of exclusivity of breastfeeding, length of KC intervention time in clinical trials, follow-up time points, and control interventions used (eg, incubator care, being wrapped in blankets when held) across the literature. Possibilities of both overestimation and underestimation of the effect of KC on breastfeeding stem from issues such as the treatment of breastfeeding as a dichotomous variable, failure to capture information such as nipple protractility, and “standard care” conditions that include breastfeeding counseling expertise which may not accurately reflect the day to day reality of the unit.⁹ Consistency in interventions and outcomes is necessary to strengthen future research. Paradigm of Kangaroo Care in the Preterm Neonate Essay.

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