If your newborn can move one arm but not the other, they may have Erb's cerebral palsy, which is caused by a birth injury to the nerves that supply the arms, hands and fingers with movement and sensation. In 90 percent of all cases, this is caused by medical malpractice, and may be grounds for a lawsuit.
In most cases, Erb's cerebral palsy is the result of a difficult birth that would have been avoided if the doctor had properly evaluated the baby's size and performed a Cesarean section birth. Sometimes, it's caused by the application of excessive force. In either case, it's malpractice.