Abstract
-
Purpose
This study examined the effects of upright nesting compared with swaddling on physiological status, sleep duration, and feeding tolerance in preterm infants in the neonatal intensive care unit.
-
Methods
A total of 48 preterm infants, 24 per group, with gestational ages of 31 to 36 weeks, were enrolled. During the study, all infants were fed every 2 hours and did not receive sedation. Those requiring respiratory support or presenting with congenital abnormalities were excluded. At the unit level, participants were assigned to the “upright nesting” or the “swaddling” group. Physiological parameters, such as body temperature, oxygen saturation, heart rate, and respiratory rate, as well as sleep duration and feeding tolerance, were measured over 3 consecutive days. To examine group effects, time effects, and group-by-time interactions, linear mixed models were applied.
-
Results
Baseline characteristics, including sex, birth weight, and gestational age, were comparable between groups. Infants receiving upright nesting showed higher mean body temperature and oxygen saturation, lower heart rate, longer sleep duration, and improved feeding tolerance. Linear mixed models presented significant main effects of time for temperature, oxygen saturation, and heart rate, while significant group effects were presented for sleep duration and feeding tolerance. Group by time interactions were not statistically significant, suggesting favorable trends without differential change over time.
-
Conclusion
Upright nesting supports physiological stability, promotes longer sleep duration, and enhances feeding tolerance in preterm infants. Furthermore, it is a promising supportive strategy in neonatal intensive care, but larger studies are needed to confirm the results.
-
Key words: Feeding behavior; Physiological processes; Posture; Preterm infant; Sleep
INTRODUCTION
The neonatal period, defined as the first 28 days of life, is the most critical phase for a child’s survival [
1]. Globally, approximately 2.3 million neonates died within the first month of 2022, with the majority occurring in low- and middle-income countries [
2,
3]. In Indonesia, the neonatal mortality rate in 2017 was 15 per 1,000 live births [
4].
Preterm birth which is defined as delivery before 37 weeks of gestation, is a leading cause of neonatal mortality. In 2019, its complications accounted for about 35% of global neonatal deaths, with 60,000 cases recorded in Indonesia [
5,
6].
Physiological instability in preterm infants arises from underdeveloped organs. This is because immature lungs may lack surfactant, increasing the risk of respiratory distress syndrome and requiring interventions such as mechanical ventilation or surfactant therapy [
7–
9]. Furthermore, cardiovascular immaturity can cause unstable blood pressure and suboptimal perfusion [
10]. Feeding intolerance is common, due to underdeveloped gastrointestinal systems, poor sucking, and swallowing reflexes, as well as delayed gastric emptying [
11,
12].
Proper positioning plays a key role in supporting physiological stability, feeding tolerance, and sleep quality [
13]. Upright nesting with swaddling places the infant in a supported semi-upright position within a nest, maintaining optimal posture and promoting neuromuscular development [
14–
16]. This intervention may enhance respiratory efficiency, improve circulation, and positively influence feeding and sleep [
17–
19].
From a theoretical perspective, upright nesting with swaddling aligns with the theory of basic human needs by Henderson [
20], emphasizing support for breathing, nutrition, and sleep. By facilitating physiological stability, improving sleep quality, and supporting feeding tolerance, the intervention helps meet these fundamental needs.
Although previous studies suggest benefits of upright nesting, evidence remains limited regarding its effects on physiological parameters, sleep duration, and feeding tolerance [
21–
23]. Assessing these outcomes is critical for optimizing care and developing evidence-based protocols to improve preterm infant health and reduce long-term complications. This study hypothesizes that upright nesting with swaddling will result in better physiological stability, longer sleep duration, and improved feeding tolerance compared to standard swaddling.
METHODS
Ethical statements: This study was approved by the Institutional Health Research Ethics Committee, Faculty of Medicine, Universitas Indonesia–Cipto Mangunkusumo Hospital (Protocol No. 24101504-KET.01/UN2.F1/ETIK/PPM.00.02/2025). Written informed consent was obtained from the parents or legal guardians of all participants.
1. Study Design
This study adopted a quantitative research method with a quasi-experimental design. Participants were assigned to either the intervention or control group, which allowed for a comparison of outcomes. Due to the nature of the intervention (upright nesting with swaddling), blinding of participants and care providers was not feasible, as the positioning procedures were visibly different. In this study, outcome assessors were blinded to group allocation to minimize bias. Although random assignment was not adopted, the design enabled examination of intervention effects and maintained a practical and ethical method. This provided valuable insights and reduced potential bias in outcome comparison. This study was reported in accordance with the Transparent Reporting of Evaluations with Nonrandomized Designs (TREND) guidelines.
2. Population and Sample
The study population consisted of infants admitted to the neonatal intensive care unit (NICU) at Cipto Mangunkusumo Hospital (RSCM), Jakarta, with a gestational age of 31 to 36 weeks. In the process, data collection was conducted from November to December 2024.
Using consecutive sampling, all eligible infants admitted during the study period were assessed based on predefined inclusion criteria. The required sample size was calculated using G*Power software ver. 3.1.9.7 (Heinrich-Heine-Universität Düsseldorf), assuming a medium effect size (F=0.25) based on previous studies examining positioning interventions in preterm infants, with repeated measures across three time points, and a statistical power of .80. A total of 48 infants were included in the study to account for a potential attrition rate of 10%.
Group allocation was conducted using a quasi-random method based on odd–even admission numbers. This led to 48 neonates divided equally into the “upright nesting” and the “swaddling” groups. To minimize potential selection bias associated with non-random assignment, baseline characteristics of both groups were assessed and confirmed to be comparable. Standardized inclusion criteria and consistent clinical protocols were applied across to ensure homogeneity and reduce confounding effects, thereby supporting the internal validity of the study within the NICU clinical setting.
3. Participants
Eligibility criteria included infants admitted to the NICU at Cipto Mangunkusumo Hospital (RSCM), Jakarta, with a gestational age of 31–36 weeks, on a 2-hour feeding schedule, and not receiving sedation. Exclusion criteria comprised infants requiring respiratory support or presenting congenital abnormalities. Prior to data collection, parents or legal guardians received detailed explanations regarding study procedures, potential risks, and benefits. Participation was voluntary, and confidentiality of all collected data was strictly maintained. Participants were allocated to either the “upright nesting (intervention)” or “swaddling (control)” group. This was conducted based on the admission sequence and using a quasi-random method, with infants assigned according to odd or even numbers. Baseline measurements were collected before the intervention, and the assessment was repeated every 20 minutes for a total of 160 minutes. Follow-up assessments continued for 3 consecutive days to monitor physiological parameters, sleep duration, and feeding tolerance.
4. Measurements
1) Physiological outcomes
Physiological outcomes included body temperature, heart rate, respiratory rate, and oxygen saturation. All parameters were measured with continuous bedside monitoring systems routinely used in the NICU. Body temperature was determined using a skin temperature probe connected to the bedside monitor and recorded in degrees Celsius (°C). Heart and respiratory rates were continuously monitored through cardiorespiratory monitoring electrodes and recorded in beats per minute (bpm) and breaths per minute, respectively. Oxygen saturation (SpO2) was measured using pulse oximetry with an appropriately sized neonatal sensor attached to the infant's foot or hand and expressed as a percentage (%). All parameters were continuously monitored during each 160-minute session over 3 consecutive days. Values were recorded according to standardized NICU monitoring protocols to ensure measurement consistency across participants.
2) Behavioral outcomes
In this study, behavioral outcomes included sleep duration and feeding tolerance. Sleep duration was assessed through continuous direct observation by trained neonatal nurses during each 160-minute observation session. Onset of sleep was defined as the absence of spontaneous motor activity with closed eyes and regular breathing patterns. Awakening was defined as eye-opening, accompanied by body movement or crying. Total sleep duration was calculated in minutes per session to ensure consistency and accuracy across observations. Furthermore, feeding tolerance was evaluated by monitoring vomiting frequency during the 3-day observation period. Episodes of vomiting were documented in the medical record immediately after occurrence, while feeding intolerance was operationally defined as the presence of one or more vomiting episodes during the observation period. To ensure fidelity, both the intervention (upright nesting group) and control (swaddling group) positions were supported using comfortable elastic cloths. Medical personnel and family members receive standardized training to ensure correct and consistent positioning throughout the study period.
5. Intervention
The intervention group received a standardized upright nesting position combined with swaddling. Neonatal nurses were trained on the positioning technique, safety criteria, and monitoring procedures prior to implementation.
Infants were placed in a semi-upright position at approximately 30° to 45° relative to the horizontal plane. This was visually in line with the incubator backrest and positioning aids to support respiratory function and gastrointestinal activity while maintaining physiological stability. Nesting support was constructed using rolled towels and soft foam arranged in a U-shape to promote midline orientation, flexion, and postural containment. The head and trunk were maintained in a neutral position, with slight neck flexion to ensure airway patency.
Swaddling was applied using a soft elastic cotton cloth around the shoulders, trunk, and lower extremities. Tension was snug but non-restrictive, with sufficient chest expansion verified by allowing the insertion of two fingers between the chest and cloth.
The intervention was administered once daily for 3 consecutive days and 160 minutes per session following routine feeding. Physiological parameters were continuously monitored, while position integrity, infant comfort, and stability were assessed every 20 minutes by trained nurses. The intervention was immediately discontinued when signs of distress, desaturation, or physiological instability occurred.
The control group received standard care consisting of a supine position combined with swaddling. Infants were positioned flat on their backs in the incubator, with the head maintained in a neutral midline position without elevation. Swaddling was applied using the same type of soft elastic cotton cloth and technique as in the intervention group to ensure consistency, with non-restrictive tension allowing adequate chest expansion. The duration and frequency of care were equivalent to the intervention group, with infants observed for 160 minutes per session over 3 consecutive days following feeding. Routine monitoring of physiological parameters and infant comfort was conducted at regular intervals by neonatal nurses in accordance with NICU protocols.
6. Statistical Analysis
All quantitative data were analyzed using IBM SPSS Statistics for Windows ver. 26.0 (IBM Corp.). Data normality was assessed through visual inspection of histograms and Q–Q plots, complemented by Shapiro-Wilk and Kolmogorov-Smirnov tests. To address the study questions on differences between the “upright nesting” and “swaddling” groups over the 3-day observation period, separate linear mixed models (LMMs) were applied to each dependent variable. Specifically, individual LMMs were applied to body temperature, heart rate, respiratory rate, oxygen saturation, sleep duration, and feeding tolerance (measured by vomiting frequency). This method allowed each outcome to be analyzed independently while accounting for repeated measurements within subjects. LMMs were selected because the models account for repeated measures within individuals, accommodate missing observations, and provide greater flexibility than traditional two-way analysis of variance for longitudinal NICU data. For each model, fixed effects included group (upright nesting group vs. swaddling group), time (Day 1, Day 2, Day 3), and the group×time interaction, while a random intercept was specified to account for individual variability among infants. A two-sided significance level of .05 was applied, and partial eta squared (η2) was reported as a measure of effect size. No missing data were observed in this study; hence, no imputation or data handling procedures were required.
RESULTS
1. Demographic and Baseline Characteristics
Participant progression throughout the study is presented in
Figure 1. The demographic and baseline characteristics of the “upright nesting (intervention)” and “swaddling (control)” groups were comparable (
Table 1). In the upright nesting group, 12 infants (50.0%) were male, and 12 (50.0%) were female, while in the swaddling group, 13 (54.2%) were male and 11 (45.8%) were female, with no significant difference between groups (
p=.999). The mean birth weight was 1,710.83±454.8 g in the upright nesting group and 1,774.58±407.5 g in the swaddling group (
p=.611). The mean gestational age was 32.29±0.999 weeks and 32.21±1.318 weeks, respectively (
p=.806). These results showed that both groups were homogeneous at baseline.
Descriptive statistics for physiological outcomes across the 3-day observation period are presented in
Table 2, while the results of the LMMs are summarized in
Table 3.
1) Body temperature
Infants in the “upright nesting” group demonstrated consistent increases in body temperature over the 3 days of observation. Body temperature had a significant effect of time (F=4.87, p=.009, partial η2=0.077), reflecting changes across the 3 days in both groups. However, there was no significant group effect (F=1.52, p=.223) or group×time interaction (F=0.92, p=.402).
This suggested that “upright nesting” group did not differ significantly from “swaddling” group in influencing temperature regulation. Although these decreases were not statistically significant, “swaddling” group may have a mild cooling effect that warrants attention in infants susceptible to temperature instability.
2) Oxygen saturation
Oxygen saturation showed a significant effect of time (F=3.21, p=.043, partial η2=0.052). No significant differences were observed between groups (F=0.56, p=.457) or in the group×time interaction (F=0.67, p=.513). This signified the similar patterns of oxygenation changes in both groups over time.
3) Heart rate
The “upright nesting” intervention group led to notable reductions in heart rate, suggesting improved cardiovascular stability. Heart rate showed a significant time effect (F=5.34, p=.006, partial η2=0.084), reflecting variation across the observation period. However, neither the group effect (F=2.18, p=.145) nor the group×time interaction (F=1.03, p=.361) was statistically significant.
4) Respiratory rate
For respiratory rate, no statistically significant effects were observed for group (F=0.72, p=.399), time (F=2.88, p=.060), or group×time interaction (F=0.49, p=.615). This signified no meaningful differences between “upright nesting” group and “swaddling” group in respiratory patterns.
3. Behavioral Outcomes
1) Sleep duration
A significant group effect was observed for sleep duration (F=13.67, p<.001, partial η2=0.191). This suggested that infants in the “upright nesting” group had longer sleep duration. However, the time effect (F=2.41, p=.093) and group×time interaction (F=0.53, p=.589) were not statistically significant, suggesting a consistent difference between groups across the 3 days.
2) Feeding tolerance
Feeding tolerance showed a significant group effect (F=4.28, p=.043, partial η2=0.069). This suggested a better tolerance in the “upright nesting” group compared to the “swaddling” group. No significant time effect (F=1.06, p=.349) or group×time interaction (F=0.32, p=.725) was observed.
DISCUSSION
The present study examined the effects of upright nesting compared with traditional swaddling on physiological and behavioral outcomes in preterm infants. Upright nesting was associated with improved thermal stability, reductions in heart rate, modest improvements in oxygen saturation, longer sleep duration, and better feeding tolerance over the 3-day observation period. These results suggest that developmentally supportive positioning may positively influence multiple domains of physiological and behavioral regulation in preterm infants receiving care in the NICU. Recent studies have similarly emphasized the growing role of structured developmental positioning strategies in optimizing physiological stability [
24-
26].
From a theoretical perspective, the results are interpreted using the theory of basic human needs by Henderson [
20]. This emphasizes the nurse’s role in assisting individuals in maintaining physiological balance until independence is achieved [
27]. Based on observation, preterm infants have limited capacity to regulate essential needs such as breathing, thermoregulation, sleep, and nutrition due to physiological immaturity [
7]. Upright nesting, as a developmentally supportive positioning strategy, may facilitate optimal body orientation, support respiratory mechanics, enhance thermal stability, promote restorative sleep, and improve feeding tolerance. As a result, contemporary neonatal care frameworks increasingly recommend individualized positioning as part of developmental care models in the NICU [
24].
In terms of thermoregulation, infants in the upright nesting group had more stable body temperature patterns over the observation period. This result is clinically relevant, as preterm infants are highly vulnerable to heat loss due to immature thermoregulatory mechanisms [
28]. Studies emphasizing developmentally supportive positioning have reported that appropriate postural orientation can contribute to improved physiological stability and reduced energy expenditure [
25]. More recent investigations have further underscored the role of nesting and supportive positioning in minimizing stress-related thermal fluctuations in preterm infants [
27,
29].
Regarding respiratory outcomes, upright nesting was associated with modest improvements in oxygen saturation and more stable respiratory rate patterns. Semi-upright positioning has been shown to promote better airway patency, improved thoracoabdominal synchrony, and enhanced lung expansion [
30]. Recent clinical observations suggest that structured positioning protocols may enhance short-term respiratory efficiency in medically stable preterm infants [
26]. Although the magnitude of oxygen saturation changes in this study was modest, even small improvements in oxygenation can reduce cumulative physiological stress in vulnerable infants.
Based on observation, cardiovascular stability appeared to be influenced by positioning. Infants in the upright nesting group showed greater reductions in heart rate, suggesting improved autonomic regulation and physiological calming [
28]. Although swaddling is often used to promote soothing and containment, it did not present comparable changes in heart rate. This result shows that postural orientation and semi-upright positioning contribute meaningfully to autonomic stabilization in preterm infants.
In this study, respiratory rate responses varied across the observation period. Upright nesting appeared to support short-term stabilization of breathing patterns, while effects in the swaddling group were inconsistent. Similar results have been reported in recent studies examining positioning-related modulation of respiratory stability in preterm infants [
28]. However, longer-term investigations are required to determine sustained clinical impact.
Behavioral outcomes further support the potential benefits of upright nesting. Infants positioned upright showed longer sleep duration across all observation days. Improved sleep may be related to enhanced physiological stability and reduced discomfort, including decreased risk of gastroesophageal reflux. Recent neonatal sleep studies also suggest that developmentally suitable positioning may enhance sleep continuity and reduce arousal frequency in preterm infants [
16,
22,
23]. Although swaddling mimics the intrauterine environment and may support sleep initiation, it appeared less effective in promoting sustained sleep duration and continuity in this study [
23].
In this study, feeding tolerance was more favorable in the upright nesting group. Semi-upright positioning may support coordinated swallowing and digestion, thereby reducing regurgitation and improving feeding efficiency [
8,
10,
15]. A recent study has further shown that positioning during and after feeding may significantly influence reflux-related symptoms and feeding stability in preterm infants [
29]. Although feeding tolerance is multifactorial and influenced by gestational age, gastrointestinal maturity, and feeding protocols, positioning represents a modifiable and clinically feasible factor.
From a clinical practice perspective, these results have several implications. Upright nesting appears to be a low-cost, non-invasive intervention that can be implemented using standard NICU materials with appropriate staff training. Recent high-quality evidence, including a Cochrane systematic review, has emphasized the potential role of infant positioning in promoting developmental outcomes and reducing morbidity in preterm infants [
30]. However, translation of this evidence into routine clinical practice requires standardized positioning protocols, structured staff education, and continuous safety monitoring to ensure consistent and appropriate application. Ongoing monitoring of crucial signs remains essential, particularly for infants requiring respiratory support or experiencing clinical instability. Furthermore, all positioning strategies should comply with established airway safety and safe sleep principles to minimize the risk of unintended adverse events.
In this study, there are several limitations that need to be acknowledged. The sample size was relatively small and recruited from a single NICU, which may limit the generalizability of the results to other clinical settings or populations. The observation period was restricted to 3 consecutive days, preventing conclusions regarding longer-term outcomes such as growth trajectories, neurodevelopmental progress, or sustained physiological regulation. Feeding tolerance was assessed solely based on vomiting frequency, without inclusion of additional clinically relevant indicators such as gastric residual volume, abdominal distention, or feeding volume tolerance. Furthermore, caregiver and staff perceptions regarding the feasibility, workload, and practical acceptability of the intervention were not evaluated.
There are no serious adverse events observed during the study period. No infants required permanent discontinuation of the intervention due to physiological instability. Temporary interruptions were performed when signs of mild instability (e.g., brief desaturation or discomfort) were observed. Infants were stabilized according to NICU protocols before resuming standard care. The frequency of these kinds of events was minimal and comparable between groups. Considering these limitations, the observed changes in oxygen saturation and respiratory rate should be interpreted cautiously as supportive trends rather than definitive evidence of sustained clinical benefit.
Despite the limitations, the results suggest that upright nesting may be a feasible and supportive positioning strategy for preterm infants in the NICU. Rather than implying superiority over existing practices, it can be considered an adjunctive intervention tailored to the individual needs and clinical conditions of preterm infants. Nurses should continue to apply comprehensive clinical assessment when selecting positioning strategies, taking into account each infant’s tolerance, medical stability, and safety considerations. Further study with larger, multicenter samples and longer follow-up periods is required to confirm the results and clarify the role of upright nesting in neonatal care.
CONCLUSION
In conclusion, upright nesting represented a feasible and supportive positioning method for preterm infants in the NICU. The intervention was associated with patterns of improved physiological stability, including thermoregulation, heart rate regulation, sleep duration, and feeding tolerance. It played a role in developmentally supportive nursing care when applied with appropriate clinical monitoring.
Upright nesting needs to be considered as an adjunctive positioning strategy rather than a replacement for established neonatal care practices. Clinical decisions should continually be guided by comprehensive nursing assessment, with careful consideration of each infant’s tolerance, medical condition, and safety. Further study with larger samples, randomized designs, and extended follow-up is needed before definitive clinical recommendations can be established.
ARTICLE INFORMATION
Figure 1.Flow diagram of participant progression through the study phases, including enrollment, group allocation, follow-up, and data analysis.
Table 1.Comparison of demographic and pretest variables between upright nesting and swaddling groups (N=48)
|
Characteristic |
Upright nesting (n=24) |
Swaddling (n=24) |
p
|
|
Sex |
|
|
1.00 |
|
Male |
12 (25.0) |
13 (27.1) |
|
|
Female |
12 (25.0) |
11 (22.9) |
|
|
Weight (g) |
1,710.83±454.8 |
1,774.58±407.5 |
.611 |
|
Gestational age (wk) |
32.29±0.999 |
32.21±1.318 |
.806 |
Table 2.Descriptive statistics of physiological and behavioral outcomes for upright nesting and swaddling groups across 3 days
|
Outcome |
Group |
Day 1 |
Day 2 |
Day 3 |
|
Temperature (°C) |
Upright nesting |
36.71±0.21 |
36.73±0.20 |
36.77±0.22 |
|
Swaddling |
36.67±0.25 |
36.66±0.24 |
36.70±0.23 |
|
Oxygen saturation (%) |
Upright nesting |
96.43±1.55 |
96.71±1.87 |
96.57±1.58 |
|
Swaddling |
96.10±1.28 |
95.70±1.73 |
95.67±2.16 |
|
Heart rate (bpm) |
Upright nesting |
166.79±11.75 |
152.14±10.90 |
156.21±9.75 |
|
Swaddling |
161.00±10.89 |
158.29±11.77 |
156.86±11.90 |
|
Respiratory rate (breaths/min) |
Upright nesting |
53.14±6.13 |
48.14±5.53 |
48.36±6.53 |
|
Swaddling |
51.24±6.29 |
50.14±6.31 |
49.71±6.48 |
|
Sleep duration (min) |
Upright nesting |
129.29±22.97 |
145.71±21.87 |
157.14±14.96 |
|
Swaddling |
86.90±20.76 |
88.57±21.15 |
86.90±21.78 |
|
Feeding tolerance (score) |
Upright nesting |
0.14±0.38 |
0.29±0.49 |
0.07±0.26 |
|
Swaddling |
0.83±0.74 |
0.57±0.62 |
0.69±0.67 |
Table 3.Mixed model results for physiological and behavioral outcomes: upright nesting vs. swaddling
|
Outcome |
Source |
F |
df |
p
|
Partial η² |
|
Temperature (°C) |
Group |
1.52 |
(1, 58) |
.223 |
0.026 |
|
Time |
4.87 |
(2, 116) |
.009 |
0.077 |
|
Group×time |
0.92 |
(2, 116) |
.402 |
0.016 |
|
Oxygen saturation (%) |
Group |
0.56 |
(1, 58) |
.457 |
0.010 |
|
Time |
3.21 |
(2, 116) |
.043 |
0.052 |
|
Group×time |
0.67 |
(2, 116) |
.513 |
0.011 |
|
Heart rate (bpm) |
Group |
2.18 |
(1, 58) |
.145 |
0.036 |
|
Time |
5.34 |
(2, 116) |
.006 |
0.084 |
|
Group×time |
1.03 |
(2, 116) |
.361 |
0.018 |
|
Respiratory rate |
Group |
0.72 |
(1, 58) |
.399 |
0.012 |
|
Time |
2.88 |
(2, 116) |
.060 |
0.047 |
|
Group×time |
0.49 |
(2, 116) |
.615 |
0.008 |
|
Sleep duration |
Group |
13.67 |
(1, 58) |
<.001 |
0.191 |
|
Time |
2.41 |
(2, 116) |
.093 |
0.040 |
|
Group×time |
0.53 |
(2, 116) |
.589 |
0.009 |
|
Feeding tolerance |
Group |
4.28 |
(1, 58) |
.043 |
0.069 |
|
Time |
1.06 |
(2, 116) |
.349 |
0.018 |
|
Group×time |
0.32 |
(2, 116) |
.725 |
0.006 |
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