The Historical Impact of Taboo (1980) on the Home Video Revolution
For 1980 audiences, this wasn't just sex; it was transgression. It suggested that the sexual revolution had not stopped at free love. It had come home to roost in the living room.
The early 1980s was a turning point for adult-oriented media, moving from obscure pornographic cinema into slightly more polished "art-house" adult films.
In a highly controversial sequence, Barbara acts on her impulses while her son is asleep, only to discover that the desire is deeply mutual.
The 1980 film "The Taboo" or more commonly referred as "Taboo" is a film directed by Christopher Walken. However, I think you might be referring to another film.