Preterm babies are predisposed to complications due to a variety of medical reasons. Some of the factors that put them at a higher risk for complications include:

• Less subcutaneous fat compared to a term baby
• Thinner skin
• Slow metabolic response to adaptations in environmental temperatures
• Compromised work of breathing because the accessory muscles for breathing are underdeveloped and the ribs are stiff
• Lungs that are noncompliant due to a lack of surfactant, a compound secreted by mature alveoli that increases alveolar surface tension and keeps the alveoli from collapsing during exhalation for efficient gas exchange
• Immature tissues of the preterm baby are easily damaged by excessive oxygen. Too high a concentration of oxygen causes oxygen toxicity, yet the preterm infant may require high supplementary oxygen levels. 
• Infections such as chorioamnionitis that can induce premature labor
• Increased risk of acquiring severe infections such as pneumonia, sepsis, and meningitis due to an underdeveloped immune system
• Limited blood volume; a small amount of blood loss can significantly affect tissue perfusion and blood pressure and increases the risk of hypotension and ischemic effects on multiple organs.
• The immature blood vessels cannot cope with rapid changes in blood pressures, which can cause damage to the vessels. Intraventricular hemorrhage (IVH) is common in the preterm baby when there are sudden changes in blood pressure. IVH may also originate from the intrinsic fragility of the germinal matrix vasculature due to the abundance of angiogenic blood vessels.
• Prone to hypoglycemia due to limited glucose reserves and immature endocrine and metabolic functions