Effectiveness of the Polyethylene Bag Compared With a Prewarmed Blanket for Preventing Hypothermia During Intrahospital Transfer in Premature Neonates: A Randomized Pilot Clinical Trial

Neonatal hypothermia is a major contributor to morbidity and mortality in premature infants, particularly during the period immediately following birth and during intrahospital transfer to the neonatal intensive care unit (NICU). International guidelines, including those from the World Health Organization and the Neonatal Resuscitation Program of the American Academy of Pediatrics, recommend thermal protection strategies such as the use of polyethylene bags or wraps in very low birth weight infants. However, most prior studies evaluating this intervention have not clearly differentiated outcomes by birth weight, and have primarily focused on body temperature as an outcome, with limited evaluation of other physiological parameters such as heart rate, oxygen saturation, and capillary blood glucose.

This randomized, open-label, parallel-group pilot clinical trial was conducted in the obstetric-surgical unit of a public hospital in Querétaro, Mexico. Sixty-seven premature neonates born before 37 weeks of gestation and weighing 2000 grams or less, who required immediate transfer to the NICU, were randomly assigned to an intervention group (n=33), in which a neonatal polyethylene bag was applied immediately after birth and maintained throughout intrahospital transfer, or a control group (n=34), in which the neonate was dried and wrapped in a prewarmed blanket according to standard unit protocol.

Axillary body temperature, heart rate, oxygen saturation, and capillary blood glucose were measured at three time points: within the first minute of life (baseline), during intrahospital transfer, and five minutes after NICU admission. The primary outcome was the frequency of hypothermia, defined as axillary temperature below 36.5°C, at NICU admission. Secondary outcomes included changes in heart rate, oxygen saturation, and capillary blood glucose between baseline and NICU admission.

Statistical analyses included comparison of baseline characteristics between groups, repeated-measures ANOVA to assess temporal variation of physiological parameters, and binary logistic regression and ANCOVA models adjusted for birth weight and gestational age to account for baseline imbalances between groups. This pilot study aims to provide preliminary evidence on the effectiveness and safety of the polyethylene bag intervention to inform the design of future, larger confirmatory trials.