Shortness of breath when the newborn is lying down may be caused by fever or considered to be caused by neonatal pneumonia. 1. Fever: If the newborn suffers from acute gastroenteritis, acute upper respiratory tract infection or acute central nervous system infection, it will lead to fever, which will cause the heart rate to accelerate and metabolism to increase, resulting in shortness of breath. 2. Neonatal pneumonia: neonatal pneumonia leads to alveolar lesions, causing hypoxia, there will be a compensatory increase in respiration, which is manifested in shortness of breath when lying down. Newborn shortness of breath when lying down, there may also be other reasons, it is recommended to go to the hospital in time, improve the examination to clarify the cause of the disease, under the guidance of the doctor to give targeted treatment or treatment.