I think it’s important for any mother carrying a child who was a product of rape to seek counseling from the beginning of the pregnancy. Whether to inform or not to inform would be situational, imo.

How good of an actor is a parent if her child looks like the rapist? What does she do if she starts to recoil from a child seeking motherly affection? Is it better to let the child believe that they are so undesirable that even they are not worthy of a mother’s love?

There is no fixed solution for issues like this. Seek counseling and improve self awareness to better understand and anticipate your child’s needs.