(HealthDay News) -- Babies may cry for a variety of reasons, and it's often difficult to figure out the reason for their unhappiness.

Here are signs that your baby may be in pain, courtesy of the University of Michigan Health System:

• Unusual crying: If the cry is in a different pitch than usual, if the crying lasts longer, or if the baby is crying more forcefully.
• Facial features: If the baby is squeezing the eyes shut, furrowing the brows, or has deep lines or wrinkles around the nose.
• A stiffness or tenseness to the body: If the baby has the arms and legs stretched out, or squeezes them in close. Some babies may seem unusually limp or quiet when in pain.
• Irritability: If you can't soothe the infant by the usual methods. Also, the infant may be fussy, restless and unwilling to eat or sleep