Sonja (1978)

Sonja has tried for years to give her husband a son. But the problem is not with her, it's is with him. She doesn't want to tell him that, so she has sex with her ex in order to get pregnant and give him a child. One of Sonja's friends knows about this, and with a old grudge she still has on her, she forces her to leave home for good or she will tell her husband who "his" son's biological father is.