Okami, Paul, Olmstead Richard, & Abramson Paul R.; Sexual experiences in early childhood: 18‐Year longitudinal data from the UCLA family lifestyles project; THE JOURNAL OF SEX RESEARCH ; 34 - 4(JANUARY 1997), 339-347
We present results of the first longitudinal study of long-term outcome correlates of sexual experiences in early childhood ("sex play"). Two hundred children participated in the UCLA Family Lifestyles Project (FLS), beginning at birth to the current wave of data collection at ages 17-18. ...
These results converge on earlier cross-sectional retrospective work, suggesting that the experience of childhood sex play in itself is unrelated to long-term adjustment.
Okami, Paul, Olmstead Richard, Abramson Paul R., & Pendleton Laura; Early childhood exposure to parental nudity and scenes of parental sexuality and scenes of parental sexuality; Archives of Sexual Behavior; 27(4, August 1998), 
As part of the UCLA Family Lifestyles Project (FLS), 200 male and female children participated in an 18-year longitudinal outcome study of early childhood exposure to parental nudity and scenes of parental sexuality ("primal scenes").
At age 17-18, participants were assessed for levels of self-acceptance; relations with peers, parents, and other adults; antisocial and criminal behavior; substance use; suicidal ideation; quality of sexual relationships; and problems associated with sexual relations.
No harmful "main effect" correlates of the predictor variables were found.