Cerebral palsy is caused by an injury to the brain before, during, or shortly after birth. The injury might be caused because of an infection or an accident. If the mother has a medical problem (i.e. high blood pressure or diabetes) this can also problems in the baby. There may also be problems during the birth. The baby might not get enough oxygen or the delivery might be difficult and the baby's brain may injured. Problems after birth may happen when a baby is born too soon and his or her body is not ready to live outside the mother's womb. Even babies born at the right time can have infections, or bleeding in their brain which causes a brain injury because the brain is still developing even after birth.

Erb's palsy is a birth injury that can affect 1 or all of the 5 primary nerves that supply the movement and feeling to an arm. The palsy can recover fully without surgery. The most common cause of Erb's palsy is dystocia, an abnormal or difficult childbirth or labor. Additionally, the condition can be caused by excessive pulling on the shoulders during a vertex delivery (head first) or by pressure on the raised arms during a breech delivery.