A premature infant's organs are not fully developed. The infant needs special care in a nursery until the organ systems have developed enough to sustain life without medical support. This may take weeks to months.

A premature infant will have a lower birth weight than a full-term infant. Common physical signs of prematurity include:

• Body hair (lanugo)
• Abnormal breathing patterns (shallow, irregular pauses in breathing called apnea)
• Enlarged clitoris (female infant)
• Problems breathing due to immature lungs (neonatal respiratory distress syndrome) or pneumonia
• Lower muscle tone and less activity than full-term infants
• Problems feeding due to difficulty sucking or coordinating swallowing and breathing
• Less body fat
• Small scrotum, smooth without ridges, and undescended testicles (male infant)
• Soft, flexible ear cartilage
• Thin, smooth, shiny skin, which is often transparent (can see veins under skin)

Not all premature babies will have these characteristics.

The infant may have difficulty breathing and maintaining body temperature.

Common tests performed on a premature infant include:

• Blood gas analysis
• Blood tests to check glucose, calcium, and bilirubin levels
• Chest x-ray
• Continuous cardiorespiratory monitoring (monitoring of breathing and heart rate)