Which intervention would best protect the newborn from the most common form of heat loss 1 point?

Twenty‐five studies across 15 comparison groups met the inclusion criteria (2481 randomly assigned participants; 2433 participants completing the studies). Interventions were categorised into three main groups: barriers to heat loss (18 studies ‐ 11 comparison groups), external heat sources (three studies ‐ two comparison groups), and combinations of interventions (four studies ‐ two comparison groups). We judged the quality of evidence for the main comparison group (plastic wraps or bags vs routine care) to be moderate across key clinical outcomes. For the remaining comparison groups, we derived evidence from one or two studies with small sample sizes, thereby limiting our ability to draw firm conclusions.

Barriers to heat loss category

Core body temperature (°C) on admission to the NICU or up to two hours after birth (plastic wraps or bags vs routine care): Thirteen studies comprising 1633 infants reported core body temperature in °C (rectal or axillary) on admission to the NICU or up to two hours after birth (Cardona Torres 2012; Chantaroj 2011; Farhadi 2012; Gathwala 2010; Knobel 2005; Leadford 2013; Reilly 2015; Rohana 2011; Smith 2013; Talakoub 2015; Trevisanuto 2010; Vohra 1999; Vohra 2004). Overall, plastic wraps or bags were effective in reducing heat loss for infants at < 37 weeks' gestation when compared with infants who received routine care immediately after birth in the delivery room. Each individual study showed a significant effect in favour of the intervention for core body temperature on admission to the NICU or up to two hours after birth across gestations, with the exception of a small study that showed no significant effect for the subgroup of infants at ≥ 28 and ≤ 31 weeks' gestation (Vohra 1999). Findings indicate that the effect is greater among the most immature infants. Data show a substantial level of heterogeneity within each subgroup of infants. Possible causes may lie within variations in methods used across studies, particularly with respect to "routine care", or in baseline hypothermia rates, as previously discussed. Heat loss prevention observed, despite these variations in how the standard of care was implemented between sites, demonstrates that findings are robust and generalisable across centres. A funnel plot analysis for core body temperature on admission to the NICU suggests possible publication bias with respect to smaller non‐effect studies that have not been published. Plastic wraps or bags seem to prevent rather than delay the postnatal fall in temperature with significant effects in favour of plastic wraps and bags at 1 hour, 90 minutes, and 2 hours after birth; at post stabilisation; and at 30 minutes, 1 hour, 90 minutes, and 2 hours after the initial NICU admission temperature was taken.

Hypothermia on admission to NICU or up to two hours after birth (plastic wraps or bags vs routine care): Ten studies comprising 1417 infants reported the incidence of hypothermia in intervention and control groups (plastic wrap or bag and routine care) (Cardona Torres 2012; Chantaroj 2011; Farhadi 2012; Knobel 2005; Leadford 2013; Reilly 2015; Rohana 2011; Trevisanuto 2010; Vohra 1999; Vohra 2004). Overall, plastic wraps or bags were effective in reducing risk of hypothermia for all infants at < 37 weeks' gestation when compared with those given routine care immediately after birth in the delivery room. Four infants would have to be wrapped in plastic to prevent one infant from becoming hypothermic on admission to the NICU. Most individual studies showed a significant effect in favour of the intervention (plastic wrap or bag), with the exception of Chantaroj 2011, which reported no differences in effect among infants at < 28 weeks' gestation; however few infants were included in this subgroup. The small Vohra 1999 and Cardona Torres 2012 studies showed borderline significant effect in favour of the plastic wrap or bag group. Reductions in risk of hypothermia varied across gestational age groups, with 33% overall, 30% for infants at < 28 weeks' gestation, and 83% for infants at 28 to 32 weeks' gestation.

Hyperthermia on admission to NICU or up to two hours after birth (plastic wraps or bags vs routine care): Twelve studies comprising 1523 infants reported the incidence of hyperthermia in intervention and control groups (plastic wrap or bag and routine care) (Cardona Torres 2012; Chantaroj 2011; Farhadi 2012; Gathwala 2010; Knobel 2005; Leadford 2013; Reilly 2015; Smith 2013; Talakoub 2015; Trevisanuto 2010; Vohra 2004; Vohra 1999). Each individual study showed no significant differences in risk of hyperthermia, with the exception of the large pragmatic 'real‐world' multi‐centre study, which showed that plastic wrap significantly increased the risk of being hyperthermic (core body temperature ≥ 37.5° C) on admission to the NICU and at post stabilisation for infants at ≥ 24 and < 28 weeks' gestation (Reilly 2015). Overall, plastic wraps or bags significantly increased the risk of hyperthermia on admission to the NICU for infants at < 37 weeks' gestation when compared with those given routine care, with highest risk seen among infants at < 28 weeks' gestation. Twenty‐five infants would have to be wrapped in plastic to have one infant hyperthermic on admission to the NICU. Five studies (Chantaroj 2011; Gathwala 2010; Leadford 2013; Talakoub 2015; Vohra 1999) included in the meta‐analysis reported no occurrence of hyperthermia in either group, and one further study reported that two infants in the wrap group were hyperthermic within the first 12 hours of life (Rohana 2011). Reilly 2015 reported that the risk of hyperthermia did not appear to be related to delivery room temperature.

Core body temperature outside the normothermic range on admission to the NICU or up to two hours after birth (plastic wraps or bags vs routine care): To balance reduced risk of hypothermia with increased risk of hyperthermia, we meta‐analysed data for the outcome measure 'incidence of core body temperature outside normothermic range on admission to NICU or up to two hours after birth'. This outcome was reported by or was derived from definitions of hypothermia and hyperthermia provided by five studies comprising 1048 infants (Chantaroj 2011; Farhadi 2012; Leadford 2013; Reilly 2015; Trevisanuto 2010). Investigators defined normothermia as core body temperature (rectal or axillary) 36.5°C to 37.5°C (Chantaroj 2011; Farhadi 2012); core body temperature (axillary) 36.5°C to 37.4°C (baseline) (Reilly 2015); core body temperature (axillary) 36.4°C to 37.5°C (Trevisanuto 2010); and core body temperature (axillary) 36.5°C to 37.5°C at one hour after birth (Leadford 2013). Most individual studies showed a significant effect in favour of the intervention (plastic wrap or bag group), with the exception of Chantaroj 2011, which showed no differences in effect among infants at < 28 weeks' gestation; however the number of infants in this subgroup was very small. Trevisanuto 2010 showed a borderline significant effect in favour of the plastic wrap or bag group for infants at < 29 weeks' gestation. Overall, for infants at < 37 weeks' gestation, plastic wraps or bags significantly reduced the risk of having a core body temperature outside the normothermic range on admission to the NICU. Overall, five infants would have to be wrapped in plastic to prevent one infant from having a core body temperature outside the normothermic range, increasing to seven for infants at < 28 weeks' gestation.

Mortality ‐ death within hospital stay or at six months' corrected gestation (plastic wraps or bags vs routine care): Ten studies comprising 1447 infants provided insufficient evidence to suggest that plastic wraps or bags significantly reduce risk of death during hospital stay (or at six months' corrected age) for all gestations.

Morbidity (plastic wraps or bags vs routine care): For infants at ≥ 24 and < 28 weeks' gestation, plastic wraps or bags significantly reduced the risk of pulmonary haemorrhage during hospital stay. Data show no evidence of a significant difference for any of the following reported secondary outcomes: incidence of: brain injury (major brain injury), bronchopulmonary dysplasia (BPD), gastrointestinal perforation, intubation in the delivery room, steroids for BPD, necrotising enterocolitis (NEC), patent ductus arteriosus (PDA), pneumothorax, requirement for bubble continuous positive airway pressure (CPAP) or ventilation, respiratory distress syndrome, ROP, and sepsis (late or early), nor for arterial oxygen saturation, bicarbonate, first blood gas pH, blood glucose concentration, median or mean duration of hospitalisation, median duration of CPAP, mean duration of oxygen therapy, and median duration of ventilation.

Emerging evidence based on two or fewer studies (plastic wraps or bags or caps vs routine care): Plastic wraps were also effective in reducing heat losses (without an increase in risk of hyperthermia) on admission to the NICU for infants at < 37 weeks' gestation with birth weight ≤ 2500 grams undergoing interhospital transport from multiple maternity homes and hospitals to a tertiary care regional referral NICU when compared with those given routine care (one study comprising 96 infants; Bhavsar 2015). Four infants would have to be wrapped in plastic to prevent one from becoming hypothermic. Plastic wraps were also effective in reducing the risk of hypoglycaemia within two hours of birth when compared with routine care (Bhavsar 2015). Data show no significant differences in the following reported secondary outcomes: base excess, blood gas pH, mean duration of oxygen therapy, blood glucose level, and severe metabolic acidosis.

One study comprising 60 infants compared plastic bag with previous drying versus routine care as opposed to most of the studies in Comparison 1 (plastic wrap or bag vs routine care), in which infants were placed in plastic wraps or bags while still wet (Cardona Torres 2012). For infants at ≥ 28 and < 37 weeks' gestation with birth weight ≥ 1000 and ≤ 2499 grams, data show significant effects favouring the plastic wrap or bag with previous drying at 30 minutes, 1 hour, 90 minutes, and 2 hours after birth. No infants were hyperthermic in the plastic wrap or bag with previous drying groups nor among those receiving routine care. Data show no significant differences in any of the reported secondary outcomes: median glucose concentration at 120 minutes after birth, heart rate, respiratory rate, or blood pressure.

Plastic caps were also effective in reducing heat losses for the younger group of infants at < 29 weeks' gestation compared with routine care (one study comprising 64 infants; Trevisanuto 2010). Infants in the routine care group were placed in prewarmed towels after drying (no head covering). Two infants would have to wear a plastic cap to prevent one infant from becoming hypothermic, and to prevent one infant from having a core body temperature outside the normothermic range (core body temperature 36.4°C to 37.5°C) on admission to the NICU. No infants had hyperthermia in the plastic cap group nor among those receiving routine care. Data show no significant differences in reported secondary outcomes: major brain injury, mortality, bicarbonate, blood gas pH, first serum glucose concentration, and intubation in the delivery room.

Two studies comprising 122 infants‐Talakoub 2015; Tescon‐delos Santos 2012 ‐ compared plastic bags + plastic caps versus routine care for infants at ≥ 28 and ≤ 32 weeks' gestation (Talakoub 2015), nor for infants at ≥ 28 and ≤ 36 weeks' gestation (Tescon‐delos Santos 2012). Overall, the combination of plastic bags + plastic caps was effective in reducing heat losses on admission to the NICU compared with routine care. Heterogeneity was high owing to differences in gestational age across studies. The combination of plastic bags + plastic caps was not effective in reducing heat losses for more mature infants at ≥ 28 and ≤ 36 weeks' gestation up to one hour after the initial NICU admission temperature was taken (Tescon‐delos Santos 2012), but this combination was effective for less mature infants at one and two hours after the initial NICU admission temperature was taken (Talakoub 2015). Data show no significant differences in risk of hyperthermia for infants at ≥ 28 and ≤ 36 weeks' gestation on admission to the NICU (Tescon‐delos Santos 2012). Researchers provided limited reporting of prespecified secondary outcomes for this comparison group and no evidence of a significant difference for any of the reported secondary outcome measures ‐ hyponatraemia or weight (grams) on the fifth day of life ‐ nor for adverse occurrences.

Emerging evidence based on two or fewer studies (stockinette cap vs routine care): When the barrier to heat loss was a stockinette cap (one study comprising 40 infants; Roberts 1981), data show a borderline statistically significant difference in temperature on admission to the NICU in favour of the intervention group for infants at ≥ 32 and ≤ 36 weeks' gestation with a birth weight < 2000 grams, but no difference for infants at ≥ 2000 grams. This finding is consistent with those reported by Greer 1988, which compared various head coverings under radiant warmers for infants > 2500 grams. When head coverings were applied within one minute of birth, infants wearing stockinettes had lower mean core body temperature at 5, 15, and 30 minutes after delivery as compared with the hatless group or the group wearing an insulated fabric bonnet. As a result, researchers did not recommend stockinettes for use in conjunction with a radiant warmer (Greer 1988).

Emerging evidence based on two or fewer studies (barrier vs barrier): Plastic bags with previous drying were shown to be comparable to plastic bags without previous drying for infants at ≥ 28 and < 37 weeks' gestation with birth weight ≥ 1000 and ≤ 2499 grams (one study comprising 60 infants; Cardona Torres 2012). Data show no evidence of a significant difference for any of the reported secondary outcomes of hyperthermia or glucose concentration at 120 minutes of life, heart rate, respiratory rate, or blood pressure.

When plastic caps were compared with plastic wraps (no cap) for infants at < 29 weeks' gestation (one study comprising 64 infants; Trevisanuto 2010), data show no significant differences between the two interventions for core body temperature on admission to the NICU and a borderline significant difference at one hour after the initial admission temperature was taken. However, use of oximetry signified opening of the bag during placement of the sensor, which could have reduced the temperature protective effect. Data show no significant differences for reported secondary outcomes: hyperthermia on admission to the NICU, major brain injury, mortality, bicarbonate concentration, blood gas pH, first serum glucose concentration, and intubation at birth.

Caglar 2014 (one study comprising 59 infants) demonstrated that plastic bags were more effective in reducing heat losses than plastic wraps at 20 minutes, 40 minutes, and 1 hour after birth among infants at ≤ 32 weeks' gestation. However, data show no significant differences between the two interventions in risk of hypothermia within one hour after birth. Investigators reported no additional secondary outcomes.

Doglioni 2014 (one study comprising 100 infants) compared plastic total body wraps (body + head) versus plastic body wraps (head uncovered) for infants at < 29 weeks' gestation. Data show no significant differences between the two interventions for core body temperature on admission to the NICU and at one hour after admission. Investigators reported no significant differences in reported secondary outcomes: hyperthermia, mortality (death before discharge), major brain injury, BPD, and NEC.

For infants at ≥ 28 and ≤ 32 weeks' gestation, the combination of plastic bags + plastic hats was shown to be more effective in reducing heat losses on admission to the NICU and at one and two hours after admission when compared with plastic wraps + cotton hats (one study comprising 64 infants; Talakoub 2015). No hyperthermic infants were included in either group. Investigators reported no additional secondary outcomes. A recent randomised controlled trial (RCT) conducted in Malaysia compared the polyethylene cap 'NeoCap' versus a cotton cap as an adjunct to polyethylene occlusive body wrap (without drying) for 80 infants at 24 to 34 weeks' gestation (Shafie 2017). This study reported no significant differences in mean NICU admission (axillary) temperatures (35.3°C vs 35.1°C; P = 0.36); however, mean poststabilisation temperature (after respiratory support, peripheral lines, and cardiorespiratory monitor probes had been secured) was significantly higher in the NeoCap group (36.0°C vs 35.5°C; P = 0.01). Rates of admission hypothermia were high in both groups (axillary temperature < 36.5°C) at 92.5% (NeoCap group) versus 100% (control group). The mean ambient delivery room temperature was 23.3°C throughout this study and may have been a contributing factor.

External heat sources category

Emerging evidence based on two or fewer studies (skin‐to‐skin care (SSC) vs routine care): SSC was shown to be effective in reducing risk of hypothermia when compared with conventional incubator care for infants with birth weight ≥ 1200 and ≤ 2199 grams (one study comprising 126 infants; Bergman 2004). Two infants would have to receive SSC to prevent one infant from becoming hypothermic (skin temperature < 35.5°C). No evidence showed a significant difference for the reported secondary outcome hypoglycaemia.

Emerging evidence based on two or fewer studies (thermal mattress vs routine care): Two studies comprising 126 infants compared thermal mattress versus routine care (Brennan 1996; Chawla 2011). Thermal (transwarmer) mattress significantly kept infants ≤ 1500 grams warmer and reduced the incidence of hypothermia on admission to the NICU with no significant difference in risk of hyperthermia. Three infants would have to receive a thermal mattress to prevent one infant from being hypothermic (core body temperature < 36°C) on admission to the NICU. Thermal (transwarmer) mattress also significantly reduced risk of a core body temperature outside the normothermic range (36.5°C to 37.5°C) on admission to the NICU. Two infants would have to receive a thermal mattress to prevent one infant from having a temperature outside the normothermic range. Data show a high level of heterogeneity between studies in this comparison group; the most likely reason for this is that the two studies used different methods. Chawla 2011 used additional thermal care measures (plastic bag without drying below the neck) for infants at < 28 weeks' gestation; this was considered to be part of routine thermal care practices. However, Brennan 1996 ‐ the earlier study ‐ did not employ such additional thermal care measures. Data show no evidence of a significant difference for any of the reported secondary outcomes: mortality, major brain injury, BPD, mean duration of: hospital stay, ventilation or oxygen requirement, incidence of hypoglycaemia, metabolic acidosis, NEC, or sepsis.

Combination of interventions category

Emerging evidence based on two or fewer studies (thermal mattress vs plastic wraps or bags): Two studies comprising 77 infants compared thermal mattresses versus plastic wraps or bags for infants at ≤ 28 weeks' gestation. Each individual study showed no significant difference in effect for core body temperature, incidence of hypothermia, hyperthermia, and core body temperature outside the normothermic range on admission to the NICU. Mathew 2012 tended towards favouring plastic bags, whereas Simon 2011 showed borderline significance favouring thermal mattresses for core body temperature on admission to the NICU. The most plausible reason for the observed moderate heterogeneity lies with Simon 2011, in which variability of use between practitioners when the intervention was polyethylene wrap and, in some cases, displacement of the wrap could have resulted in heat loss. Data show no significant differences for reported secondary outcomes: brain injury, major brain injury, mortality, BPD, hypotension, NEC, PDA, ROP, spontaneous intestinal perforation, worst base deficit, and worst pH in the first 24 hours of life.

Emerging evidence based on two or fewer studies (plastic bags and thermal mattresses vs plastic bags): Two studies comprising 119 infants compared plastic bag + thermal mattress versus plastic bag (Leslie 2007; McCarthy 2013). Investigators reported that plastic bags in combination with thermal mattresses were shown to keep infants warmer on admission to the NICU when compared with plastic bags alone for infants at < 31 weeks' gestation (Leslie 2007; McCarthy 2013), and greater effect size was seen for infants at < 28 weeks' gestation. However, overall, data show no significant difference in risk of hypothermia (core body temperature < 36.5°C) but an overall significant increased risk of hyperthermia associated with the simultaneous combination of plastic bag and thermal mattress. For every six infants receiving plastic bag + thermal mattress, one infant would be hyperthermic on admission to the NICU for infants at < 31 weeks' gestation. Researchers found no significant difference in risk of having a core body temperature outside the normothermic range on admission to the NICU nor for reported secondary outcomes: major brain injury, mortality, chronic lung disease, coagulation support, inotrope use, intubation during admission, and one or more doses of surfactant during admission.

Overall for all included interventions designed to prevent heat loss at birth

Despite variation in interventions applied; definitions of 'routine care' and definitions of hypothermia, hyperthermia, and normothermia; and groups of infants included, a similar pattern emerged across all studies, with infants in the intervention group significantly warmer (or showing a non‐significant trend in that direction) than infants receiving 'routine care'. Evidence of moderate quality shows that plastic wraps or bags keep preterm infants warmer and lead to higher temperatures on admission to neonatal units with less hypothermia and temperatures outside the range of normothermia. Extremely preterm infants (< 28 weeks' gestation) appeared to benefit the most. Other interventions such as thermal mattresses, skin‐to‐skin care, and plastic caps also reduce hypothermia risk when compared with routine care, but these findings are based on two or fewer studies with small sample sizes. One small study found that stockinette caps were not more effective when compared with routine care in infants at 32 to 36 weeks' gestation.

Hyperthermia in the newborn may be caused by intrapartum maternal fever or, as our evidence suggests, by use of interventions to reduce hypothermia in the delivery room. Animal and human studies suggest that hyperthermia is harmful to the newborn brain. In infants at ≤ 6 hours' postnatal age and at ≥ 36 weeks’ gestation with moderate or severe hypoxic‐ischaemic encephalopathy, elevated temperatures were associated with increased odds of death or moderate/severe disability at 18 to 22 months on secondary data analysis of the NICHD whole body cooling trial (Laptook 2008a). Lyu 2015, in a retrospective observational study of 9833 preterm infants at < 33 weeks’ gestation in the Canadian Neonatal Network, demonstrated a U‐shaped relationship between admission temperature and poor clinical outcome. The lowest rates of adverse outcomes were associated with temperatures between 36.5°C and 37.2°C. Hyperthermia has also been shown to worsen ventilator‐induced lung injury and inflammation in preterm lambs (Ball 2010). Therefore, iatrogenic hyperthermia should be avoided, particularly in infants at risk of neurological injury. Caution must be taken to avert iatrogenic hyperthermia, particularly when multiple interventions are used simultaneously immediately after birth in the delivery room (e.g. plastic bags + thermal mattresses).

Many observational studies (as discussed in the Background section) have demonstrated increased mortality among preterm hypothermic infants compared with those who maintain normothermia, yet evidence is insufficient to suggest that interventions to prevent hypothermia reduce risk of in‐hospital mortality across all comparison groups included in this review. In addition, researchers have provided limited evidence of benefit and no evidence of harm for most short‐term morbidity outcomes known to be associated with being hypothermic, including major brain injury, BPD, ROP, NEC, and nosocomial infection. Limitations include lack of power to detect effects of these interventions on morbidity and mortality across most comparison groups. Data show significant differences for only two morbidity outcomes. For infants at ≥ 24 and < 28 weeks' gestation, plastic wraps or bags significantly reduced risk of pulmonary haemorrhage during hospital stay when compared with routine care (moderate‐quality evidence). Plastic wraps were also more effective in reducing risk of hypoglycaemia within two hours of birth when compared with routine care for infants at < 37 weeks' gestation with birth weight ≤ 2500 grams undergoing interhospital transport in one small study. Further investigation is needed to explore the pathways from admission hypothermia to mortality, and to ascertain whether hypothermia is a step in the causal pathway (Laptook 2008), possibly via late sepsis (Laptook 2007); alternatively, hypothermia may be a marker for illness and poorer outcome by association rather than for causality.

No reported adverse events across all studies, such as skin maceration or infection, were attributable to the intervention, nor did plastic bags, plastic caps, skin‐to‐skin care, or thermal mattresses interfere with resuscitation practices. However, mixed reports have discussed plastic wraps with regard to interference with resuscitation and placing of umbilical lines and probes. Problems appear to be related to displacement of plastic wraps.

Although the interventions studied in this review offer some short‐term benefit regarding heat loss prevention in vulnerable preterm and/or low birth weight infants, their effect on morbidity and their long‐term safety remain largely unknown; however, the harmful effects of hypothermia are well documented, and the findings of this review demonstrate that hypothermia can be prevented. Further information on effects of plastic wraps on long‐term neurodevelopmental outcomes will become available upon full publication of follow‐up data from the Heat Loss Prevention (HeLP) study (Reilly 2015). Therefore, monitoring (for both benefits and risks of potential adverse events) should continue in neonatal units where such interventions are adopted as routine practice, because wide variation in clinical practice has been reported. In addition, clarification of 'normal' temperatures for these populations of infants is essential, as are better data correlating axillary versus rectal versus other temperature‐taking sites. The multi‐centre HeLP study will yield important prospective data on 'normal' temperatures in this population, including correlation of axillary and rectal temperatures.

The 2015 neonatal resuscitation guidance provided by the American Heart Association (AHA), the European Resuscitation Council (ERC), and the International Liaison Committee on Resuscitation (ILCOR) states that for all gestational ages, admission temperature of newly born, non‐asphyxiated infants is a strong predictor of mortality and morbidity and should be recorded as an outcome predictor and as a key quality indicator (Perlman 2015). Fastman 2014 conducted a small qualitative study in the USA to explore clinicians' perspectives on barriers to management of hypothermia among low birth weight infants in the delivery room, during transport, and upon arrival to the NICU. A multi‐disciplinary team approach to neonatal resuscitation, thermal care, and overall delivery room management, coupled with integration of temperature monitoring into quality and safety programmes, was considered an important step in addressing this long‐standing problem. Paradoxically, hypothermia is a greater problem in lower‐income countries, where climates are generally warmer. Four studies were conducted in lower‐middle‐income countries: India (Bhavsar 2015; Gathwala 2010), Zambia (Leadford 2013), and the Phillippines (Tescon‐delos Santos 2012); and seven in upper‐middle‐income countries: South Africa (Bergman 2004), Mexico (Cardona Torres 2012), Thailand (Chantaroj 2011), Turkey (Caglar 2014), Iran (Farhadi 2012; Talakoub 2015), and Malaysia (Rohana 2011). Plastic wraps (food grade polyethylene, clean but not sterile) used in the HeLP study cost approximately CAD 157 for 5000 wraps, which, when calculated per infant, equates to approximately (USD) 3 cents each (Reilly 2015). Therefore, these may be an affordable option for preterm infants in low‐resource settings. Another low‐cost option would be skin‐to‐skin care; however, only one study fulfilled our inclusion criteria, because in most studies, participants were term infants, or skin‐to‐skin care was not initiated immediately at birth (Bergman 2004).

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Plastic wrap or bag compared with routine care in preterm and/or low birth weight infants