What condition does prolonged cold stress lead to in newborns?

Prolonged cold stress in newborns can lead to significant physiological changes, primarily due to the baby's inability to maintain a stable body temperature in a cold environment. When exposed to prolonged cold stress, newborns lose heat and their core temperature drops, which triggers several compensatory mechanisms.

As the newborn's body attempts to generate heat through non-shivering thermogenesis (primarily using brown fat), there is an increased consumption of oxygen for metabolism. However, if the cold exposure is severe and prolonged, it can exceed the newborn's metabolic capacity leading to hypoxia, which results in a decline in oxygen tension. This reduction in oxygen can also lead to an accumulation of lactic acid due to anaerobic metabolism, subsequently resulting in metabolic acidosis.

In summary, the combination of diminished oxygen levels and the buildup of acids from metabolic processes emphasizes the critical role of maintaining normothermia in newborns. This is why prolonged cold stress leads to both a decline in oxygen tension and increased metabolic acidosis in newborns.