A risk ...

.... of using spanking for discipline.

http://www.preventchildabuse.com/abuse.htm

What makes people abuse children?
It is difficult to imagine that any person would intentionally inflict
harm on a child. Many times, physical abuse is a result of excessive
discipline or physical punishment that is inappropriate for the
child's age. The parent may simply be unaware of the magnitude of
force with which he or she strikes a child. Most parents want to be
good parents but sometimes lose control and are unable to cope.

Factors which contribute to child abuse include the immaturity of
parents, lack of parenting skills, unrealistic expectations about
children's behavior and capabilities, a parent's own negative
childhood experience, social isolation, frequent family crises and
drug or alcohol problems. Child abuse is a symptom that parents are
having difficulty coping with their situation.