Article Text


At what weight should preterm infants be transferred from incubator to open cot?
  1. Abdul Razak1,2
  1. 1 Department of Pediatrics, Princess Nourah Bint Abdulrahman University, King Abdullah bin Abdulaziz University Hospital, Riyadh, Saudi Arabia
  2. 2 Department of Pediatrics, McMaster Childrens Hospital, McMaster University, Hamilton, Ontario, Canada
  1. Correspondence to Dr Abdul Razak, Division of Neonatology, Department of Pediatrics, Princess Nourah Bint Abdulrahman University, King Abdullah bin Abdulaziz University hospital, Riyadh 13412, Saudi Arabia; razakmdpaed{at}; arazak{at}

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A preterm infant born at 28 weeks’ gestation is 5 weeks old, weighs 1600 g and nursed in an incubator. During the round, the medical team instructs the nurse to transfer the infant to open cot. The nurse in charge is concerned that weaning the infant from incubator to cot at this weight might affect the temperature stability, weight gain and may delay the discharge of the infant. The third-year paediatric resident offers to review the literature and report the findings to the multidisciplinary team.

Structured clinical question

In a medically stable preterm infant with a birth weight of less than 1600 g, not on any respiratory support, nursed in incubator (patient), whether transferring the infant from incubator to unheated open cot at a lower weight (<1700 g) (intervention) compared with a higher weight (>1700 g) (comparison) will affect the temperature stability, weight gain and length of hospital stay of the infant (outcomes)?


Study selection

Randomised or quasirandomised clinical trials, systematic reviews and observational studies comparing two or more different weights for transferring the infant from incubator to cot were included. Included studies should report one or more outcomes mentioned above in the question. Descriptive studies, conference abstracts, letter to the editor and case series were excluded.

Search strategy

PubMed and Cochrane CENTRAL databases were searched from inception to 4 December 2018 for following terms: ((neonate) OR (preterm) OR (premature) OR (infant) OR (low birth weight)) AND ((weaning) OR (transfer) OR (discontinue)) AND ((incubator) OR (cot)). The search returned 118 abstracts (PubMed: 105 records and Cochrane CENTRAL: 13 records). The references of the included studies were also searched. The list of studies excluded following a detailed review, including the reasons for exclusion, are provided in online supplementary file 1. Three systematic reviews,1–3 five randomised controlled trials4–8 and three observational studies9–11 were identified for inclusion (figure 1).

Figure 1

Study flow diagram outlining stages of search results and filtering process (as per Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines).


Table 1 summarises the details of the included studies. The evidence described comes from five randomised clinical trials and three observational studies that compared two or more different weight categories to identify the body weight threshold for transferring the infants from incubator to cot. Most studies compared weaning the infant at a body weight of 1600 g to a body weight of 1800 g. Of the five randomised clinical trials,4–8 four trials4–6 8 were evaluated in the Cochrane systematic reviews. The Cochrane review is not updated to include the largest randomised controlled trial7to date. Hence, an updated fixed-effect model meta-analysis was performed using Review Manager V.5.3 (Cochrane Collaboration, Nordic Cochrane Centre, Copenhagen, Denmark) including the recent trial7 to provide the updated evidence. The results of meta-analyses are as shown in figure 2. The evidence from all the trials suggests that weaning at a lower body weight from incubator to cot is safe and does not affect temperature stability and weight gain. Infants weaned at a lower body weight grew significantly better than infants weaned at a higher weight.3 6 7 10 Besides, the proportion of infants returning to an incubator because of temperature instability did not differ if weaned at a lower body weight compared with a higher body weight. However, weaning the preterm infant at a lower body weight does not necessarily resulted in earlier discharge.3 6 7 The updated meta-analyses concur with the findings from the Cochrane systematic reviews (figure 2). Only one trial identified infants weaned to cot at a lower body weight were able to discharge early compared with infants who weaned at a higher body weight.4 The population in this trial4 was slightly older (gestational age ~32 weeks) compared with the randomised trials,6 7 which failed to show reduced length of hospital stay (gestational age ~30–31 weeks). Similarly, an observational study10 identified infants length of stay is shorter if weaned from incubator to cot at a lower body weight; however, the study groups differ for baseline prognostic factors and hence should be interpreted with caution.

Figure 2

Forest plots for comparison: transfer from incubator to cot at a lower weight (>1600 g) versus higher weight (>1800 g), outcomes: weight gain (g/kg/day) post-transfer (A), proportion of infants with returning to incubator (B) and length of hospital stay from randomisation until  discharge (C).

Table 1

Summary of included studies comparing lower body weight versus higher body weight for transferring preterm infant from incubator to unheated open cot

Preterm infants resting energy expenditure increases significantly once transferred from incubator to cot that might affect the weight gain.12 Contrary to this belief, the trials demonstrated improved weight gain in infants transferred to cots at a lower body weight than infants transferred at a higher body weight. It is interesting to identify why infants transferred from incubator to cot earlier than later should grow better as opposed to become poor. It is speculated that preterm infants transferred earlier to cot might be benefited with positive perceptions from the families and caregivers viewing as ‘a normal baby’,9 improved parental bonding, improved support for social development6 and more access to infants resulting in improved quality in the feeding and rates of skin-to-skin care. The randomised clinical trials do not provide the data on breastfeeding proportion and duration, caloric intake and duration of kangaroo care to justify this speculation.

One of the essential criteria to discharge preterm infants is the ability to maintain their body temperature after weaning from the ambient temperature support. It is unknown at what weight the preterm infants can regulate their body thermoregulation. The weight criteria of 1700–1800 g to transfer a preterm infant from incubator to cot is arbitrary and based on the professional experiences of the clinicians.13 Some neonatal units consider transferring infants at a lower weight of 1600–1700 g or below, whereas other units consider transferring infants at a higher weight of 1700 g or above.11 The question raised in this review provides the evidence from the observational studies, randomised clinical trials and systematic reviews, which suggest preterm infants can maintain their body temperature if weaned from incubator to cot at a lower body weight with no harm. The evidence does not favour towards discharging infants early or reducing the hospital stay by weaning them to cot at a lower body weight. It is presumable that infants transferred to cot earlier might be able to go home sooner if they can maintain their body temperature; however, it may not be true.4 6 Preterm infants should also demonstrate the full oral feeding for them to discharge.6 The feeding milestone influenced by the gestational age and is the last milestone to be achieved in preterm infants younger than 32 weeks’ gestation.14 Hence, even though preterm infants successfully transferred from incubator to cot, they may not get discharged if the oral feeding is unachieved earlier. It is also important to note that the definition of the length of stay is considerably different between studies (table 1).

Certain limitations should be acknowledged before we conclude on the evidence. Of the five included randomised clinical trials,4–8 significant methodological limitations were identified in two trials.5 8 The methodological quality was good among the three randomised trials.4 6 7 These trials were sufficiently powered for primary outcomes and were at low risk of selection, reporting and attrition biases.4 6 7 However, among these three trials,4 6 7 it was not possible to blind the caregivers who might have introduced performance bias (lower body weight group infants cared more judiciously than higher body weight group) resulting in downgrading the quality of evidence. Similarly, the observational studies suffer the risk of selection bias. In these observational studies, clinicians might have opted infants to be transferred from incubator to cot at a lower weight who look ready to be moved. On the contrary, infants who do not seem ready might have been weaned later at a higher weight. In addition to this, the precision for few outcomes is poor (smaller sample size) despite pooling the results in the meta-analyses. Apart from this, the quality of evidence is also affected by the significant heterogeneity for some outcomes. It is also noteworthy that the cohort included in the trials is moderate preterm infants, and hence caution is exercised for generalising the results to extremely preterm infants. Similarly, the cohort in the included studies was sampled across level 3 neonatal intensive care units mostly, and some level 2 neonatal units, in developed countries (table 1). Hence, the results are less generalisable to infants receiving care in less developed countries. Despite these limitations, the evidence still seems acceptable justifying that preterm infants can be transferred from incubator to cot at a lower body weight of 1600 g.

Clinical bottom line

  • Preterm infants who are medically stable can be transferred from incubator to open unheated cot once they reach a body weight of 1600 g and above (grade B).

  • Weaning preterm infants from incubator to cot at a lower body weight of 1600 g is accompanied with higher weight gain post-transfer compared with weaning at a higher body weight of 1800 g (grade B).


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  • Contributors AR solely conceptualised and designed the study, performed the search and initial screening of the articles, abstracted the data, drafted the manuscript and approved the final version.

  • Competing interests None declared.

  • Provenance and peer review Not commissioned; externally peer reviewed.

  • Patient consent for publication Not required.

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