A review of 124 studies confirmed that kangaroo-care newborns did all of the following except:

Breastfeeding outcomes

Six studies with 711 women reported the number exclusively breastfeeding at hospital discharge to one month post birth; SSC infants were more likely to be breastfeeding at that time (average RR 1.30, 95% CI 1.12 to 1.49; I² = 44%; moderate‐quality evidence) (Analysis 1.6). Results from this meta‐analysis should be interpreted with caution due to moderate heterogeneity for this outcome. All heterogeneity disappears when we remove the Thukral 2012 trial, which measured exclusive breastfeeding at 48 hours post birth (analysis not shown).

Three studies with 245 women examined breastfeeding status (using the Index of Breastfeeding Status (IBS) at one month postpartum. The IBS (Hake‐Brooks 2008; Labbok 1990) is a single‐item indicator and consists of three major levels of breastfeeding exclusivity ‐‐ full, partial, and token breastfeeding. Full breastfeeding is divided into two subcategories. In exclusive breastfeeding, the first subcategory, the infant consumes only breast milk and no other liquid or solid food. The second is almost exclusive breastfeeding where infants are given water, juice, vitamins and minerals infrequently in addition to breast milk. Partial breastfeeding is divided into four subcategories – high, medium‐high, medium‐low and low. In high partial breastfeeding more than 80% of the infant’s diet is composed of breast milk, in medium‐high 50% to 80%, in medium‐low 20% to less than 50%, and in low less than 20%. In token breastfeeding, the breast is used primarily as a source of comfort for the infant. Breastfeeding is occasional and irregular, less than 15 minutes a day. The infant is weaned when no longer receiving any breast milk. The eight patterns of IBS are ranked as one for exclusive and two for almost exclusive breastfeeding, three for high, four for medium‐high, five for medium‐low and six for low partial breastfeeding. Token breastfeeding is ranked seven and weaning is ranked eight. All scores were reversed for this analysis so that a higher score indicated more exclusive breastfeeding. There was no clear evidence of differences between groups for this outcome, and results varied considerably between studies; therefore the overall average treatment effect should be interpreted with caution (MD 0.86, 95% CI ‐0.73 to 2.44; participants = 245; studies = three; I² = 90%; Analysis 1.8).

Different hospital care protocols for women and infants in treatment and control arms contribute to the high heterogeneity for this outcome. The mothers in the Punthmatharith 2001 study delivered in a Baby Friendly Hospital in Thailand with 24‐hour rooming‐in for all healthy infants. SSC began 60 minutes post birth and the infants received (M = 30 minutes) of SSC. Control mothers held their swaddled infants after the episiotomy repair. Most of the SSC took place in extremely warm, un‐air conditioned eight‐bed postpartum rooms with frequent visitors so that contextual issues, such as body warmth and modesty, may have changed SSC desirability and also effectiveness. There were no between‐group differences in breastfeeding status in this trial. In Moore 2005, SSC infants were held a mean of 99.5 minutes and swaddled control infants a mean of 60 minutes and both groups were assisted with the first breastfeeding in the delivery room. Moore 2005 suggested that barriers to long‐term breastfeeding that exist in the USA, especially the customary absence of, or very brief, paid maternity leave, attenuated the effectiveness of early SSC on breastfeeding status day 28 to one month post birth. In Shiau 1997, mothers began SSC at four hours post birth and held their infants in SSC eight hours daily for three days. Control mothers began breastfeeding 24 hours post birth and they fed their infants every four hours in the nursery. In this trial there was a large difference in breastfeeding status favoring the SSC group.

More infants were exclusively breastfeeding six weeks to six months post birth in seven studies (n = 640) (average RR 1.50, 95% CI 1.18 to 1.90; participants = 640; studies = seven; Analysis 1.7;moderate‐quality evidence). There was considerable heterogeneity for this outcome: Chi² = 15.92, P = 0.01, I² = 62%, so results should be interpreted with caution. Heterogeneity is likely due to the different time points at which breastfeeding was measured.

Two small studies reported no group differences in breastfeeding at one year post birth (RR 6.19, 95% CI 0.82 to 46.78; participants = 62; studies = two; Analysis 1.9).

Four studies with 384 women examined breastfeeding effectiveness scores and those in the SCC group had higher mean scores (IBFAT score MD 2.28, 95% CI 1.41 to 3.15; participants = 384; studies = four; Analysis 1.10), but there was moderate heterogeneity for this outcome: Chi² = 5.05, P = 0.17, I² = 41%. The Infant Breastfeeding Assessment Tool (IBFAT) evaluates four parameters of infant suckling competence: infant state of arousal or readiness to feed; rooting reflex; latch‐on; and suckling pattern. The infant can receive a score of 0 to 3 on each item for a maximum total score of 12 indicating adequate suckling competence (Matthews 1988; Matthews 1991). An IBFAT > 10 is considered successful, and a 2.69 difference in score between treatment groups represents a 22% difference in score and may be clinically meaningful.

Five studies found that infants held SSC were more likely to breast feed successfully during their first feeding post birth than those who were held swaddled in blankets by their mothers. 'Successful' meant an IBFAT 10 to 12 or BAT 8 to 12, and the mix of instruments probably contributed to the considerable variability between findings in these five studies (n = 575) (average RR 1.32, 95% CI 1.04 to 1.67; heterogeneity Tau² = 0.05, P < 0.00, I² = 85%) (Analysis 1.11).

Thukral 2012 reported similar group rates of successful breastfeeding (BAT > 8); we did not include these data in the meta‐analysis because the outcome was measured at 36 to 48 hours post birth rather than during the first breastfeeding (intervention 10/17 and controls 11/18).

In a single study with data for 88 women, Bystrova 2003 reported the number of infants that suckled within two hours of the birth; there was no clear evidence of differences between groups (RR 1.06, 95% CI 0.83 to 1.35; participants = 88; studies = one) (Analysis 1.12).

Maternal breast temperature

Bystrova 2003 found higher breast temperatures and variability in temperatures 30 to 120 minutes post birth in mothers who held their infants SSC than those who were separated from their infants (MD 0.60, 95% CI 0.34 to 0.86; participants = 132; studies = one) (Analysis 1.13). Duration of SSC was 95 minutes. The researchers suggested that the variations in maternal breast temperature in the SSC group may regulate infant temperature more effectively than stable breast temperatures and help prevent neonatal hypothermia, but we do not regard such minimal difference in temperature as clinically meaningful.

Breast problems

Breast engorgement pain (measured by the self‐reported Six Point Breast Engorgement Scale (Hill 1994) or by the mother's perception of tension/hardness in her breasts) was less for SSC than non‐SSC mothers on day three post birth (SMD ‐0.41, 95% CI ‐0.76 to ‐0.06; participants = 131; studies = two; I² = 8%) (Analysis 1.14) (Bystrova 2003; Shiau 1997). As a rule of thumb, an SMD of 0.41 represents a moderate difference (Guyatt 2013).

Girish 2013 reported breast engorgement as a dichotomous variable, with 2/50 women in the intervention group reporting engorgement versus 1/50 in the standard care group.

Infant physiological outcomes

Infant heart rate and respiratory rate

Four studies (Christensson 1992; Mazurek 1999; Nolan 2009; Villalon 1992) obtained data on infant respiratory rate 75 minutes to two hours post birth, and three studies obtained data on infant heart rate. SSC infants had a lower mean heart rate than control infants who were separated from their mothers although the evidence of a difference between groups was not clinically meaningful and there was high heterogeneity for this outcome (MD ‐3.05 beats per minute (BPM), 95% CI ‐7.84 to 1.75; 183 infants); (heterogeneity: Tau² = 15.26, P = 0.0005, I² = 87%) (Analysis 1.15). Results also favored SCC infants for respiratory rate but again these results were not clinically meaningful and there was considerable variability in findings between studies (MD ‐3.12 RPM, 95% CI ‐6.61 to 0.37; 215 infants) (heterogeneity Tau² = 9.24, P = 0.004, I² = 77%) (Analysis 1.16). Heterogeneity was mainly due to findings from the Villalon 1992 study; as stated above, findings at different time points varied considerably in this study. We carried out sensitivity analysis where results for this study were excluded; for both heart rate and respiratory rate, removal of findings for Villalon 1992 favored the SCC groups and reduced heterogeneity, but differences were not clinically meaningful (heart rate MD ‐5.77, 95% CI ‐7.43 to ‐4.11; respiratory rate MD ‐4.76, 95% CI ‐6.12 to ‐3.41) (Analysis 1.30; Analysis 1.31).

Bergman 2004 compared the number of infants in the two groups who did not exceed physiological parameters for stability requiring medical attention. The five parameters were infant skin temperature less than 35.5 ºC on two consecutive occasions, heart rate less than 100 or more than 180 BPM on two consecutive occasions, apnea more than 20 seconds, oxygen saturation less than 87% on two consecutive occasions, blood glucose less than 2.6 mmol/L and FIO2 up to 0.6 with continuous positive airway pressure (CPAP) up to 5 cm of water pressure. Fifteen of the 18 SSC and one of the 13 control infants did not exceed parameters (RR 10.83, 95% CI 1.63 to 72.02; participants = 31; studies = one). The most common reasons for exceeding parameters in control infants were hypothermia, hypoglycemia, and respiratory problems (Analysis 1.17). There are too few infants in this analysis to make meaningful conclusions.

Neonatal intensive care unit (NICU) admissions

There were no differences between groups in infant admissions to the NICU (RR 0.51, 95% CI 0.20 to 1.26; participants = 305; studies = two; Analysis 1.18). Two studies with 42 infants (Chwo 1999; Syfrett 1993) examined hospital length of stay in late preterm infants 34 to 36 weeks' gestational age and found no between group differences, and there was high heterogeneity for this outcome (MD ‐95.30, 95% CI ‐368.50 to 177.89; participants = 42; studies = two; I² = 84%) (Analysis 1.20).

Infant body weight change

No group differences were found in infant body weight change day 14 post birth; this outcome was reported in two studies with 43 infants (MD ‐8.00 g, 95% CI ‐175.60 to 159.61) (Analysis 1.19) (Chwo 1999; Moore 2005). Infant weight change per kilogram per day was not reported in any of the included studies. Infant weight outcomes were reported in a number of different ways in the more recent trials and the data could not be added to the pre‐specified weight outcomes.

Girish 2013 reported infant weight loss at three days postpartum (mean 18 g SD 6 g intervention group and mean 23 g SD 9 g in the standard care comparison group).

Thukral 2012 reported infant weight at 48 hours (intervention group 2714 g SD 220 g n = 20; control group 2574 g SD 275 g n = 21) with P value 0.11.

Srivastava 2014 reported weight loss at hospital discharge as a percentage of birthweight (intervention 4.01 % SD 2.0 n = 122 and control group 6.12 % SD 2.6 n = 118).

Infant crying/behavior

Christensson 1995 found that 12 of the 14 SSC infants cried no more than one minute during the 90‐minute observation compared with only one of the 15 control infants (RR 12.86, 95% CI 1.91 to 86.44; participants = 29; studies = one; Analysis 1.21). Mazurek 1999 found that SSC infants cried for a shorter length of time during a 75‐minute observation period than control infants (MD ‐8.01, 95% CI ‐8.98 to ‐7.04; participants = 44; studies = one) (Analysis 1.22).

Other outcomes

Mothers who held their infants SSC indicated a strong preference for the same type of post‐delivery care in the future (average RR 6.04, 95% CI 2.05 to 17.83; participants = 439; studies = three; I² = 85%) compared to those who held their infants swaddled (Analysis 1.25). However, there was high heterogeneity for this outcome.

Mothers who held their infants SSC displayed less state anxiety day three post birth, though we are unsure of the clinical meaning of this difference (SMD ‐0.32, 95% CI ‐0.59 to ‐0.04; participants = 390; studies = three; I² = 31%) (Analysis 1.26). As a rule of thumb, an SMD of 0.32 represents a small effect (Guyatt 2013). Shiau 1997 used the state anxiety scale from the State Trait Anxiety Inventory (STAI) (Spielberger 1970). The state anxiety scale is a 20‐item instrument that measures how the individual feels in the present moment and is measured on a Likert scale from one = not at all to four = very much so, with possible range from 20 to 80 and higher indicating more anxiety.

One trial could not be included in the meta‐analysis of maternal state anxiety due to the direction of the scale being opposite to that of other trials. Khadivzadeh 2009 reported anxiety with their own scale (no minimum or maximum stated); a higher score meant less anxiety, and women with SSC therefore reported less anxiety (mean 28.2 SD 3.32 n = 46) than did women with standard care (26.07 SD 4.16 n = 46). We cannot interpret this result due to insufficient information in the trial report.

Parenting confidence scores were measured in a single study with data for 20 women; there was no evidence of meaningful differences between groups (MD 5.60, 95% CI ‐6.24 to 17.44; participants = 20; studies = one; Analysis 1.27). The Parenting Sense of Competence Scale is a 17‐item scale developed by Gibaud‐Wallston 1977 that assesses an individual’s perceptions of their skills, knowledge, and abilities for being a good parent, their level of comfort in the parenting role, and the importance they attribute to parenting. Individuals rate their level of agreement from one (strongly disagree) to six (strongly agree) on each item. Higher scores indicate that the individuals feel more confident about their parenting abilities, with range of possible scores 17 to 102.

Non‐prespecified outcomes

A large number of additional outcomes were measured in the included studies. Most of these outcomes were measured in single studies. The clinical importance of results for many such outcomes is difficult to determine. Outcomes that appeared similar were measured in a range of different ways, in addition, many outcomes were reported at different or multiple time points and results may not have been consistent within or between studies. Non‐prespecified outcomes reported include observed mother and infant behavior during the first few hours after birth, outcomes relating to breastfeeding (e.g. duration of first feed and number of breastfeeding problems) and a range of outcomes relating to mother‐child interaction.

Page 2

'Summary of findings Quality of the Evidence using GRADE