Neonatal Hypothermia at and after Admission: Burden and Associations with Outside Air Temperature and Neonatal Ward Temperature in Four Sub Saharan African Countries Implementing with the NEST360 Alliance

Background: Annually, 2.3 million newborns die, largely from preventable causes. Neonatal hypothermia is an important contributor to morbidity and mortality, particularly in low-resource settings. This study quantified the burden of hypothermia at and after admission in four NEST360-supported countries and examined associations between outside air temperature, ward temperature, and neonatal hypothermia. Methods: We conducted a retrospective analysis of newborn admissions (January 2021 to June 2025) across 66 neonatal units in Kenya, Malawi, Nigeria, and Tanzania. Hypothermia was defined using WHO thresholds (mild: 36.0-36.4{degrees}C, moderate: 32.0-35.9{degrees}C, severe: <32.0{degrees}C). Newborn admission and lowest after admission body temperatures were extracted from routine clinical records. Ward temperatures were captured using the Hadli Monitoring System, and environmental temperatures were obtained from Open-Meteo. Multivariate ordinal logistic regression assessed associations between air temperature, ward temperature, and hypothermia at admission and during admission. Results: Among 418,458 newborn admissions with recorded admission temperatures, 47.3% (n=220,684) were hypothermic at admission (country range: 22.8%-61.9%), while 63.5% (n=48,746) experienced hypothermia during hospital stay (country range: 18.5%-74.4%), based on 76,855 admissions (July 2024-June 2025) with temperature data. Based on admission and subsequent temperature, 28.5% had no documented hypothermia, 8.6% improved to non-hypothermic status, 29.4% developed hypothermia after admission, and 33.5% experienced hypothermia at admission and during hospital stay. Across 59 neonatal units, minimum ward temperatures >26{degrees}C were maintained on 92.6% of 365 days. At admission, ward temperatures of 30-33{degrees}C were associated with 9% lower odds of a lower thermal category versus 26-28{degrees}C (p<0.01). After admission, ward temperatures of 28-30{degrees}C reduced odds by 18% (p<0.05). Warmer outside temperatures (>24{degrees}C day, >21{degrees}C night) were protective, corresponding to 19% and 68% lower odds of a lower thermal category after admission, respectively, compared with 19-24{degrees}C and 15-21{degrees}C reference groups. Newborns had 3.6-fold higher odds of hypothermia at night than during the day. Each 1{degrees}C increase in post-admission temperature reduced odds of death by 6%. Conclusion: Neonatal hypothermia remains highly prevalent despite most units maintaining ward temperatures above WHO minimum standards (26{degrees}C). Strengthening all components of the warm chain, particularly at night and during colder seasons, is essential to reduce hypothermia and improve survival.