A simple answer to this simple question is “no way.” But if you want to go deep into the topic there could be areas where you could get leads.
Sexually abused children keep their matters secret. Specially the fact that they were sexually abused. This secrecy hides them from being recognised as sexually abused. In addition, you would find that sexually abused children are silent and like to keep quiet.
An easier method to find a sexually abused child from a family is to compare the child with other children in the family. If you notice that one of the children behaves differently (less talkative, less active, less inteligent, etc.) than her/his sisters/brothers take it as a symptom of being sexually abused.
Lastly, do not be over-confident about the above measures. Not every child with the above qualities would have been sexually abused. Understanding and examinig these qualities is an easy task while judging them is the difficult part which is the most important.