Background
Newborn preterm infants lose body heat rapidly after birth, and hypothermia is a major risk factor for morbidity and mortality. Admission hypothermia (body temperature <36.5 °C at NICU admission) is common among very low birth weight (VLBW) infants. However, neonatologists often underestimate its true incidence in their own settings compared with published data.

Survey Design

We conducted a cross-sectional, international, online survey at the institutional level to assess neonatal thermal-care practices and the perceived incidence of AH among VLBW infants. A structured questionnaire was distributed to the neonatologist directors of 108 tertiary NICUs across eight collaborating counties: South Korea (n=16), Japan (n=43), Taiwan (n=7), Singapore (n=3), the Philippines (n=11), Thailand (n=20), Indonesia (n=5), and Mongolia (n=3). Respondents were asked to reflect their unit’s current practice and protocols based on 2024 standards. The survey was developed in English, finalized on July 24, 2024, and administered between April 13 and June 30, 2025, via the Google Forms platform.

Results
Basic NICU profiles in each country

NICUs were classified as very small (<20 VLBW admissions/year), small (20–49), medium (50–100), or large (>100). Across the 108 NICUs, most were classified as small-volume centers admitting 20–49 VLBW infants annually. In Japan, nearly all NICUs admitted fewer than 50 infants per year, whereas South Korea and Taiwan showed a wider distribution including several large centers. All NICUs in Singapore were high-volume, while the Philippines and Thailand demonstrated the broadest spread, with Thailand having the highest proportion of large-volume units. In Indonesia, only medium and large centers participated, and in Mongolia, the limited number of NICUs were evenly distributed across categories.

Routine neonatal resuscitation before 22 weeks of gestation was extremely rare, reported only in a few centers in Japan (4.7%) and South Korea (6.3%), but was universal in Mongolia. At 22 weeks, resuscitation was initiated in over half of Japanese NICUs (60.5%) and nearly half in South Korea (43.8%), compared with lower rates in Taiwan (28.6%) and Thailand (5%), and none in Singapore; Mongolia again reported 100%. By 23 weeks, resuscitation was routine in all South Korean centers and common in Japan (88.4%), Taiwan (71.4%), and Singapore (66.7%), though less frequent in Thailand (30%), Indonesia (40%), and the Philippines (18.2%). At 24 weeks, nearly all centers in Japan and all in South Korea, Taiwan, Singapore, and Mongolia resuscitated, with rising uptake in Thailand (70%), Indonesia (60%), and the Philippines (27.3%). By 25 weeks, resuscitation was nearly universal across all countries, exceeding 85% in every setting.

Underestimation of the Incidence of Admission Hypothermia
Published admission hypothermia incidence among VLBW infants varied substantially across Asian countries: Korea 74.1% (nationwide data), Japan 48% (single center), Taiwan 76.8% (single center), and Singapore 40.5–79.4% (single center). When surveyed, most neonatologists underestimated the actual incidence compared with these published figures. Most neonatologists perceived admission hypothermia to be infrequent, with the majority in Japan and South Korea estimating it as rare or occasional. In contrast, centers in the Philippines, Thailand, and Indonesia more often reported higher frequencies, with some estimating that hypothermia occurred in 20–49% or ≥50% of VLBW infants. Mongolia showed an even distribution of responses despite the small number of NICUs.

Written Protocols for Admission Hypothermia
Written protocols for the prevention of admission hypothermia were present in fewer than half of the participating NICUs, with an overall prevalence of 46.3% (50 of 108 units). All centers in Singapore and Mongolia (100%) reported having protocols, as did the majority in Taiwan (85.7%), Korea (81.3%), and Indonesia (80.0%). In contrast, fewer centers in Thailand (45.0%), the Philippines (27.3%), and Japan (20.9%) reported established written protocols.

Current interventions: Delivery-Room Practices
All 108 centers reported using a preheated radiant warmer at birth, but only five Japanese NICUs resuscitated VLBW infants under a heated incubator. Setting the NICU ambient temperature above 25 °C before delivery was widely adopted (>80% overall), nearly universal in Japan (93.0%), South Korea (87.5%), the Philippines (90.9%), Thailand (75.0%), and fully adopted in Singapore, Indonesia, and Mongolia, but less common in Taiwan (42.9%). Resuscitation in a preheated incubator was frequent in South Korea (87.5%), the Philippines (81.8%), Thailand (60.0%), Indonesia (100%), and Mongolia (66.7%), but lower in Japan (48.8%), Taiwan (28.6%), and Singapore (33.3%). Head covering was routine in most countries (>80%), except Japan (14.0%) and Singapore (66.7%). Polyethylene plastic wrap was widely used (>90% in most countries, 72.1% in Japan), while commercial products (e.g., Neohelp®) were uncommon outside South Korea (62.5%) and Mongolia (100%). Heated humidified air for ventilation showed variable uptake, highest in South Korea (68.8%) and Japan (55.8%), and lowest in Singapore (33.3%). Preheated transport incubators were consistently used in most countries (>95%), except the Philippines (54.5%) and Mongolia, where all centers instead practiced skin-to-skin contact after resuscitation.

Monitoring temperature and temperature recommendations

Placement of a temperature probe during resuscitation was relatively uncommon, reported by only a few centers in South Korea (6.3%) and Japan (9.3%), and none in Taiwan, but was more frequent in Singapore (66.7%), the Philippines (45.5%), and Thailand (50.0%), and universally practiced in Indonesia and Mongolia (100%). The site of initial temperature measurement at NICU admission varied widely: Korea (87.5%), Indonesia (80.0%), and Mongolia (100%) mainly used the axilla, whereas Thailand predominantly used the rectum (85.0%). Japan and Taiwan showed mixed practices between axillary and rectal sites, while Singapore and the Philippines favored the axilla but with one-third also using the rectum. Continuous temperature monitoring after admission was inconsistently implemented. When used, probes were most often placed on the abdomen, particularly in Singapore, Thailand, Indonesia, and Mongolia (all 100%), while Japan, Taiwan, and the Philippines reported greater variability in probe sites, and a minority of centers in these countries did not use continuous monitoring at all.

Most centers reported recommended ambient temperature guidelines for delivery rooms (≥25 °C) and operating rooms (≥24 °C), with some Japanese institutions adopting higher thresholds (≥30 °C). Delivery room recommendations were reported by the majority of centers in South Korea (81.3%), Japan (72.1%), and Taiwan (57.1%), and universally in Singapore, the Philippines, Thailand, Indonesia, and Mongolia. On NICU admission, most centers targeted ambient temperatures ≥24 °C, with incubators set at ≥29–30 °C. Daily ambient temperature logs were maintained in Korea (68.8%), Japan (44.2%), Taiwan (14.3%), and universally in Singapore. For operating rooms, uptake was high in Korea (75.0%), Japan (74.4%), and Taiwan (71.4%), and universal in all other countries. Recommendations for NICU ambient temperature were even more common, reported by 87.5% of Korean, 83.7% of Japanese, and 71.4% of Taiwanese centers, with universal adoption in Singapore, Thailand, Indonesia, and Mongolia; the Philippines showed slightly lower uptake (72.7%).

Humidification Practices
Recommended incubator humidity was highest for the most immature infants, with most centers targeting 90–100% at 23–24 weeks or <600 g, particularly in Korea, Japan, Taiwan, Singapore, and Thailand. For infants at 25–27 weeks or 700–999 g, high humidity remained common, though more centers in the Philippines, Thailand, Indonesia, and Mongolia used 70–79% or 80–89%. By 28–32 weeks or 1,000–1,500 g, recommended humidity levels shifted lower, with 60–79% more frequently adopted, especially in Taiwan, Singapore, and Mongolia. These findings highlight a consistent trend of decreasing humidity targets with increasing gestational age and birth weight.

Discussion/Conclusion

This multinational survey reveals substantial heterogeneity in thermal care practices for VLBW infants across Asian NICUs. While most centers adopted basic interventions such as preheated warmers and polyethylene wraps, notable gaps remained in the use of preheated incubators, heated humidified gases, and continuous monitoring. Fewer than half of units had written protocols, and daily ambient temperature logging was inconsistent, despite the well-documented association between admission hypothermia and adverse outcomes. Importantly, neonatologists tended to underestimate the true incidence of hypothermia in their own settings compared with national or single-center data, suggesting insufficient prioritization of preventive strategies. Countries with higher adoption of standardized protocols and bundled interventions, such as Singapore and Mongolia, demonstrated more consistent practices, highlighting the feasibility of system-level approaches. Variations in humidity and temperature thresholds also indicate progress toward evidence-based care, but wide inter- and intra-country differences underscore the need for harmonization. To close the gap between evidence and practice, region-wide quality improvement efforts—including standardized care bundles, written protocols, regular audits, and harmonized guidelines—are urgently required. Such coordinated strategies would reduce preventable hypothermia, improve outcomes for VLBW infants, and promote equity of care across diverse health systems.

Acknowledgement

We are deeply grateful to all participating hospitals and their NICU teams for their time and invaluable contributions to this survey.