The Third Circuit has deferred to the Board of Immigration Appeals' definition of a crime of child abuse. In addition, the Court found that a Pennsylvania conviction for unlawful contact with a minor meets this definition, even though it criminalizes mere communication with a minor, because the communication must be for the purpose of an illicit sexual act, and thus, poses a significant risk of harm to the child.
The full text of Mondragon-Gonzalez v. Attorney General can be found here: