Role of Polyethylene Bag in Prevention of Hypothermia in Preterms and Low Birth Weight Infants

Neonatal hypothermia is defined as a core body temperature below 36.5°C, it represents a serious thermal emergency in the immediate postnatal period.¹ The transition from intrauterine to extrauterine life poses unique thermoregulatory challenges, especially for vulnerable neonates who lack adequate physiological reserves to counter rapid heat loss.²  Globally, hypothermia is recognized as a “silent emergency,” affecting between 32% and 85% of newborns in different regions, with the highest prevalence reported in low- and middle-income countries.³ According to the World Health Organization (WHO), neonatal hypothermia is strongly associated with increased risks of sepsis, respiratory distress, hypoglycemia, intraventricular hemorrhage, and mortality.⁴ The burden is more pronounced in South Asia and Sub-Saharan Africa, where preterm birth rates are high and access to sophisticated neonatal intensive care facilities is limited.⁵ In Pakistan, where nearly 40% of neonatal deaths occur within the first 24 hours of life prevalence ranging from 25% to over 50% among hospitalized neonates, making it one of the leading preventable causes of neonatal mortality.⁶

Preterm and LBW infants are at a particular disadvantage due to a constellation of factors: large surface area-to-body mass ratio, thin epidermis with poor keratinization, deficient subcutaneous fat, and reduced brown adipose tissue stores. These factors not only predispose them to increased radiant, convective, conductive, and evaporative heat loss but also limit their capacity for non-shivering thermogenesis.⁷ Furthermore, immature neurological and metabolic pathways impair effective thermoregulation, while delayed initiation of skin-to-skin contact and inadequate environmental control in delivery rooms exacerbate the risk. Hypothermia, in turn, triggers a vicious cycle by increasing oxygen consumption, inducing metabolic acidosis, impairing coagulation, and suppressing immune responses.⁸

Traditional approaches for preventing neonatal hypothermia include warm delivery rooms, radiant warmers, incubators, heated mattresses, and skin-to-skin care (kangaroo mother care). While effective, these interventions may not always be feasible or immediately available, particularly in low-resource settings or during emergency deliveries.⁹ The use of polyethylene bags or plastic wraps has emerged as a simple, inexpensive, and practical strategy to reduce heat loss, especially in very low birth weight and extremely preterm infants.¹⁰ By creating a barrier to evaporative and convective heat loss, polyethylene wrapping preserves body temperature during the critical period after birth before more advanced thermal care can be initiated.¹¹

In light of the persistent challenge of neonatal hypothermia and its substantial contribution to mortality in preterm and LBW infants, evaluating low-cost interventions such as polyethylene bag use holds significant clinical and public health importance. Understanding its role in thermal regulation not only informs neonatal resuscitation protocols but also provides a feasible, scalable solution for resource-constrained environments like Pakistan, where improving neonatal survival remains a top priority.

This study was conducted in the Neonatology Department of Sughra Shafi Medical Complex Narowal from 1st February 2025 to 1st August 2025. A total of 130 preterm and low birth weight neonates were enrolled using non-probability consecutive sampling. The sample size of 130 neonates was calculated using the WHO sample size calculator. By keeping a confidence level of 95%, a power of 80%, and an expected incidence of mild hypothermia was taken as 26.6% from previous literature, the required sample size was estimated at 130.¹² Written informed consent was obtained from parents or guardians prior to enrollment.

Neonates with gestational age less than 37 weeks or birth weight below 2500 grams were included. Babies with major congenital malformations, perinatal asphyxia requiring extensive resuscitation, or those with life-threatening conditions at birth were excluded. Eligible neonates were randomized into two groups by computer-generated random numbers. Group A (intervention group) was immediately placed in a sterile polyethylene bag up to the level of the neck after birth, while Group B (control group) received standard thermal care, which included drying with pre-warmed towels, placement under a radiant warmer, and covering with caps and blankets.

All deliveries were attended by trained neonatal staff, and ambient delivery room temperature was maintained at 25–28°C. In both groups, routine neonatal resuscitation steps were carried out as per Neonatal Resuscitation Program (NRP) guidelines. Core body temperature was measured with a digital axillary thermometer at 10 minutes, 30 minutes, and 60 minutes after birth. Hypothermia was defined as body temperature less than 36.5°C, and was further classified according to WHO criteria into mild (36.0–36.4°C), moderate (32.0–35.9°C), and severe (<32.0°C). All neonates were closely monitored for cardiorespiratory stability, hypoglycemia, and other complications during the first 24 hours of life. Data regarding gestational age, birth weight, gender, mode of delivery, Apgar scores, and temperature readings at specified intervals were recorded on a predesigned proforma. Any episodes of hypothermia, need for supplemental warming, and early neonatal outcomes were documented. The primary outcome measure was the incidence of hypothermia within the first hour of life. Secondary outcomes included mean temperature differences, severity of hypothermia, and requirement of additional thermal support.

Data were entered and analyzed using Statistical Package for Social Sciences (SPSS) version 25. Quantitative variables such as gestational age, birth weight, and body temperature were presented as mean ± standard deviation. Categorical variables such as gender, mode of delivery, and presence or absence of hypothermia were expressed as frequencies and percentages. Data were stratified with respect to gestational age, birth weight, and gender. Post-stratification, chi-square test was applied to compare categorical outcomes, while independent sample t-test was used for continuous variables. A p-value ≤ 0.05 was taken as statistically significant

The baseline characteristics of the study population showed that gender distribution was comparable across the two groups, with 46.2% females and 53.8% males in the polyethylene bag group, while in the standard care group 47.7% were females and 52.3% were males. The mean gestational age was 32.6 ± 1.5 weeks in the polyethylene bag group and 32.8 ± 1.6 weeks in the standard care group. A higher proportion of infants in both groups were between 34–36 weeks of gestation (56.9% in polyethylene bag vs. 55.4% in standard care). The mean birth weight was comparable between the groups, with nearly half of the neonates in both groups weighing below 2000 g (50.8% vs. 52.3%). Thus, the baseline demographics and clinical characteristics were evenly distributed across the two groups, as given in Table 1. At one hour post-delivery, the mean temperature of neonates in the polyethylene bag group was 36.6 ± 0.3°C compared to 36.2 ± 0.4°C in the standard care group, indicating a higher maintenance of normothermia in the polyethylene bag group, as shown in Table 2.

When comparing hypothermia incidence, neonates managed with polyethylene bags demonstrated a substantially lower rate of hypothermia (27.7%) compared to those receiving standard care (70.8%). Conversely, the majority of neonates in the polyethylene bag group maintained normothermia (72.3%) compared with only 29.2% in the standard care group, as shown in Table 3. Stratification analysis revealed that hypothermia was more common in neonates with gestational age below 34 weeks, occurring in 36.4% of the standard care group versus 15.6% in the polyethylene bag group (p = 0.041). Similarly, among infants with birth weight <2000 g, hypothermia occurred more frequently in the standard care group (37.1%) compared to the polyethylene bag group (17.6%) (p = 0.038). With respect to gender, male infants in the standard care group had a higher hypothermia incidence (30.4%) compared to those in the polyethylene bag group (14.9%). A similar pattern was observed in females (29.5% vs. 13.2%) (p = 0.049). These findings emphasize the consistent protective effect of polyethylene bags across gestational age, birth weight, and gender categories, as given in Table 4.

Table 1 – Baseline Characteristics & Demographics of Study Population (n = 130)

Table 2 – Mean Temperature at 1 Hour Post-Delivery (n = 130)

Table 3 – Incidence of Hypothermia in Polyethylene Bag versus Standard Care Groups (n = 130)

Figure-I: Incidence of Hypothermia in Polyethylene Bag versus Standard Care Groups

Table 4 – Stratification of Hypothermia by Gestational Age, Birth Weight, and Gender in Study Groups

Neonatal hypothermia remains a major contributor to morbidity and mortality, particularly in preterm and low birth weight infants. Despite advances in neonatal care, heat loss immediately after birth continues to pose a significant challenge.13 Polyethylene bags offer a simple, cost-effective, and evidence-based method to reduce evaporative heat loss. Their role in preventing hypothermia is increasingly recognized as a practical intervention in both high- and low-resource settings.14

In our study, the mean temperature at one hour post-delivery was significantly higher in neonates managed with polyethylene bags (36.6 ± 0.3 °C) compared to standard care (36.2 ± 0.4 °C), and the incidence of hypothermia was substantially lower in the polyethylene bag group (27.7%) than in the standard care group (70.8%). These findings are consistent with previous studies that have demonstrated the efficacy of polyethylene bags in maintaining neonatal body temperature.

 Yalestyarini et al. (2024) reported that 93% of neonates had baseline hypothermia (<36.5 °C), and after the use of polyethylene bags, 87% experienced an increase or stabilization in temperature with a highly significant Wilcoxon test result (p = 0.000).15 Similarly, Chantaroj et al. (2019) observed higher median body temperatures in the intervention group {36.5 °C (35.5–37.2)} compared with controls {35.9 °C (34.9–36.5)}, p < 0.001, and a reduced incidence of hypothermia (26% vs. 89%, p < 0.001) with a number needed to treat of 1.58, which is comparable to our observed 43% reduction.16 Hu et al. (2018) further supported this by showing a significantly lower rate of moderate hypothermia (3.7% vs. 27.8%, RR 0.10, 95% CI 0.02–0.46, p < 0.001) and higher axillary temperatures (36.4 ± 0.4 °C vs. 35.9 ± 0.9 °C, p = 0.001), findings that closely align with our results.17 Mansour et al. (2020) also demonstrated significantly higher mean axillary temperatures in the intervention group at admission and at subsequent time points up to two hours, corroborating our findings of sustained thermoprotection.18

Possidente et al. (2023) documented a markedly lower admission hypothermia rate in the polyethylene bag group (2.6% vs. 14.7%, OR 0.14, 95% CI 0.03–0.64, p = 0.007) and higher median admission temperatures (36.8 °C vs. 36.5 °C, p = 0.001). However, they also reported a higher incidence of hyperthermia (9.2% vs. 1.0%, p = 0.023), an outcome not observed in our cohort, where no infant developed hyperthermia.19 In contrast, Ali et al. (2024) found no significant difference in overall hypothermia incidence (85.9% vs. 88.9%, p = 0.521), although polyethylene wraps significantly reduced the need for subsequent interventions (p = 0.001). This partial agreement may reflect differences in study populations, as their cohort included very preterm and very low birth weight neonates at higher baseline risk.20

Leadford et al. (2023) highlighted normothermia maintenance in 64.8% of the intervention group versus 77.8% in controls, which is different from our findings where polyethylene bags outperformed standard care. Mortality outcomes, however, did not differ significantly between groups in either study.21 Khan et al. (2021) also found significantly higher temperatures at one and two hours post-admission in the polyethylene group (<0.05), which parallels our observed one-hour temperature advantage.22 Pervaiz et al. (2023) demonstrated a higher median temperature (37.6 ± 0.7 °C vs. 36.8 ± 1.8 °C, p < 0.05) and a lower hypothermia incidence (6.5% vs. 32.6%, p < 0.05) in the intervention group, echoing our substantial reduction in hypothermia. Riaz et al. (2017) similarly reported hypothermia in 45% of the polyethylene bag group compared to 69% in controls, with a significant p value of 0.000, reinforcing the effectiveness of this intervention.23

A major strength of this study is its randomized design with an adequate sample size of 130 neonates, ensuring balanced comparison between groups. The study provides locally relevant data on hypothermia prevention, which is valuable for neonatal care guidelines in Pakistan. Use of objective temperature measurements adds reliability to the findings. However, the study was limited to a single center, which may affect generalizability. Short follow-up duration restricted assessment of long-term outcomes. Additionally, other confounding factors such as resuscitation time and ambient room temperature were not fully controlled.

Polyethylene bags were effective in reducing hypothermia among preterm and low birth weight infants compared to standard care. This low-cost, simple intervention has the potential to improve neonatal survival in resource-limited settings. Its routine adoption in delivery rooms is strongly recommended.

1.     Wainaina J, Ogero M, Mumelo L, Wairoto K, Mbevi G, Tuti T, et al. Hypothermia amongst neonatal admissions in Kenya: a retrospective cohort study assessing prevalence, trends, associated factors, and its relationship with all-cause neonatal mortality. Frontiers in Pediatrics. 2024 Mar 27;12:1272104.

2.     Saha U. General Anatomical and Physiological Considerations in the Newborn and Neonates. InClinical Anesthesia for the Newborn and the Neonate 2023 (pp. 137-204). Singapore: Springer Nature Singapore.

3.     Yitayew YA, Aitaye EB, Lechissa HW, Gebeyehu LO. Neonatal hypothermia and associated factors among newborns admitted in the neonatal intensive care unit of Dessie Referral Hospital, Amhara Region, Northeast Ethiopia. International Journal of Pediatrics. 2020;2020(1):3013427.

4.     Legesse BT, Wondie WT, Mekonen WM, Mekonnin GB. Predictors of mortality among neonates admitted with hypothermia and respiratory distress syndrome at West Oromia tertiary hospitals, Retrospective Follow-up Study, 2023. Journal of Neonatal Nursing. 2025 Jun 1;31(3):101673.

5.     Ferede YA, Tassew WC, Zeleke AM. Neonatal hypothermia and its determinants among neonates admitted to the neonatal intensive care unit in Ethiopia: a systematic review and meta-analysis. Journal of Neonatal Nursing. 2025 Feb 1;31(1):152-9.

6.     Kanhar IA, Ahsan S, Nazir S, Tariq S, Akbar T. Mortality pattern of patients in neonatal intensive care unit at Indus Hospital, Karachi. Med Forum 2023;34(2):94-97.

7.     Batra K, Pharr J, Olawepo JO, Cruz P. Understanding the multidimensional trajectory of psychosocial maternal risk factors causing preterm birth: a systematic review. Asian journal of psychiatry. 2020 Dec 1;54:102436.

8.     Dunne EA, O’Donnell CP, Nakstad B, McCarthy LK, European Society for Paediatric Research (ESPR) Neonatal Resuscitation Section Writing Group. Thermoregulation for very preterm infants in the delivery room: a narrative review. Pediatric Research. 2024 May;95(6):1448-54.

9.     Kyokan M, Rosa-Mangeret F, Gani M, Pfister RE. Neonatal warming devices: What can be recommended for low-resource settings when skin-to-skin care is not feasible?. Frontiers in Pediatrics. 2023 Apr 25;11:1171258.

10.   Abiramalatha T, Ramaswamy VV, Bandyopadhyay T, Pullattayil AK, Thanigainathan S, Trevisanuto D, Roehr CC. Delivery room interventions for hypothermia in preterm neonates: a systematic review and network meta-analysis. JAMA pediatrics. 2021 Sep 1;175(9):e210775-.

11.   Ramaswamy VV, de Almeida MF, Dawson JA, Trevisanuto D, Nakwa FL, Kamlin CO, Hosono S, Wyckoff MH, Liley HG, International Liaison Committee on Resuscitation Neonatal Life Support Task Force. Maintaining normal temperature immediately after birth in late preterm and term infants: a systematic review and meta-analysis. Resuscitation. 2022 Nov 1;180:81-98.

12.   Kumar N, Gupta H, Dhiman S, Pal A, Groover N. Prevention of neonatal hypothermia in Himalayas: kangaroo mother care for the term neonates: A randomised controlled trial. International Journal of Life Sciences, Biotechnology and Pharma Research.2023;12(4):492-96.

13.   Cordeiro RC, Ferreira DM, Reis HD, Azevedo VM, Protázio AD, Abdallah VO. Hypothermia and neonatal morbimortality in very low birth weight preterm infants. Revista Paulista de Pediatria. 2021 Oct 4;40:e2020349.

14.   Tourneux P, Durand E, Pelletier A, Ghyselen L, Bach V, Libert JP. Use of a Polyethylene Bag to Reduce Perioperative Regional and Whole‐Body Heat Losses in Low‐Birth‐Weight Neonates. BioMed Research International. 2017;2017(1):8243184.

15.   Yalestyarini EA, Taviyanda D, Muftiana E, Ningrum MP. Effect of using polyethylene plastic bags against increased and stable body temperature in low birth weight babies (LBW) in the Nicu Room of SLG Kediri Hospital. Journal Of Nursing Practice. 2024 Oct 29;8(1):215-9.

16.   Chantaroj S, Techasatid W. Effect of polyethylene bag to prevent heat loss in preterm infants at birth: a randomized controlled trial. J Med Assoc Thai. 2019 Dec 1;94(Suppl 7):S32-7.

17.   Hu XJ, Wang L, Zheng RY, Lv TC, Zhang YX, Cao Y, Huang GY. Using polyethylene plastic bag to prevent moderate hypothermia during transport in very low birth weight infants: a randomized trial. Journal of Perinatology. 2018 Apr;38(4):332-6.

18.   Mansour Moustafa Mohamed S, Samir Ahmed El-husseiny H, Mohamed Ahmed Ayed M, El-Sayed El-Ghadban F, Mohamed Amin F. Effect of polyethylene cap on hypothermia prevention among low birth weight neonates. Egyptian Journal of Health Care. 2020 Sep 1;11(3):1090-8.

19.   Possidente AL, Bazan IG, Machado HC, Marba ST, Caldas JP. Evaluation of two polyethylene bags in preventing admission hypothermia in preterm infants: a quasirandomized clinical trial. Jornal de pediatria. 2023 Oct 13;99(5):514-20.

20.   Ali B, Rahman A, Ahmad N, Aqib AR, Nasir U, Jalil A. Efficacy of Polyethylene Wrap in Prevention of Hypothermia in Very Preterm and Very Low Birth Weight Neonates at Birth: Polyethylene Wrap to Prevent Hypothermia in Prematurity. Journal of Health and Rehabilitation Research. 2024 Aug 30;4(3):1-5.

21.   Leadford AE, Warren JB, Manasyan A, Chomba E, Salas AA, Schelonka R, Carlo WA. Plastic bags for prevention of hypothermia in preterm and low birth weight infants. Pediatrics. 2023 Jul 1;132(1):e128-34.

22.   Khan GA, Riaz U, Aziz T, Iqbal S, Qureshi TA, Shafaat HK. Effectiveness of polyethylene skin wrap in prevention of hypothermia in preterm and low birth weight neonates. Pakistan Armed Forces Medical Journal. 2021 Jun 30(3):810.

23.   Pervaiz F, Iqbal M, Ejaz N, Akram M, Fatima S, Shoukat R. Frequency of Neonatal Hypothermia in Preterm Infants Wrapped with and without Plastic Bag after delivery. Pakistan Journal of Medical & Health Sciences. 2023;17(11):23-27.