He or she will appreciate the feedback and your tactful approach. If a problem arises with your nanny, remember that he or she is your employee and it's your obligation to make sure your policies are clearly understood. If this arrangement is generally working out well but you have one or two specific problems, talk them over with the nanny. If he or she subsequently follows your rules, forget the incident happened. If he or she doesn't change, you may need to look for a nanny who respects your wishes.
Child abuse is a very serious charge.
Don't make it loosely, because a simple accusation can ruin the career of an innocent provider. However, if you think your child is in danger or is being mistreated, pull him or her out of the arrangement immediately. You also have an obligation to tell the parents of the other children in the provider's care that you suspect dangerous behavior. In addition, call the state's licensing agency to report the problem. Both private and nonprofit centers usually maintain a parent board to oversee operations.