A child sexual abuse offense where the perpetrator is related to the child, either by blood or marriage, is a form of incest described as intrafamilial child sexual abuse.The most-often reported form of incest is father–daughter and stepfather–stepdaughter incest, with most of the remaining reports consisting of mother/stepmother–daughter/son incest. Father–son incest is reported less often; however, it is not known if the actual prevalence is less or it is under-reported by a greater margin. Similarly, some argue that sibling incest may be as common, or more common, than other types of incest: Goldman and Goldman reported that 57% of incest involved siblings; Finkelhor reported that over 90% of nuclear family incest involved siblings; while Cawson et al. show that sibling incest was reported twice as often as incest perpetrated by fathers/stepfathers.Prevalence of parental child sexual abuse is difficult to assess due to secrecy and privacy; some estimates state that 20 million Americans have been victimized by parental incest as children. Types
Child sexual abuse includes a variety of sexual offenses, including:

sexual assault – a term defining offenses in which an adult uses a minor for the purpose of sexual gratification; for example, rape (including sodomy), and sexual penetration with an object. Most U.S. states include, in their definitions of sexual assault, any penetrative contact of a minors body, however slight, if the contact is performed for the purpose of sexual gratification.
When first presenting for treatment, the patient can be fully aware of their abuse as an event, but their appraisal of it is often distorted, such as believing that the event was unremarkable (a form of isolation). Frequently, victims do not make the connection between their abuse and their present pathology. Prevention
Child sexual abuse prevention programmes were developed in the United States of America during the 1970s. Some programme are delivered to children and can include one-to-one work and group work. Programmes delivered to parents were developed in the 1980s and took the form of one-off meetings, two to three hours long. In the last 15 years, web-based programmes have been developed. School-based education programs were evaluated in 2015 by Cochrane that demonstrated improvements in protective behaviors and knowledge among children. Offenders
Demographics
Offenders are more likely to be relatives or acquaintances of their victim than strangers. A 2006–07 Idaho study of 430 cases found that 82% of juvenile sex offenders were known to the victims (acquaintances 46% or relatives 36%).More offenders are male than female, though the percentage varies between studies. The percentage of incidents of sexual abuse by female perpetrators that come to the attention of the legal system is usually reported to be between 1% and 4%. Studies of sexual misconduct in US schools with female offenders have shown mixed results with rates between 4% to 43% of female offenders.