I am not sure this is true. Certainly any child is not to be aborted for they are an innocent, but attempting to prevent or reduce the chances of fertilization to begin with in cases of rape would not seem to be an issue.
What is immoral about contraception in marriage is the deliberate misuse of one’s sexual faculties towards perverse ends. During rape there is a person who is coerced, violated, and forced. There is no deliberate and willful misuse of sexual faculties by the victim. If one has deliberate sex with one’s spouse one must be open to life, but I see no reason for obligation to let sperm swim its way up in cases of rape. It’s not a matter of having one’s cake and eating it, too.
I think we need to be careful of losing sight of why contraceptive practices are immoral.
If any clergy or people with degrees in moral theology wish to comment… please do. I am open to correction.
Edit: I suppose it matters about what we’re talking about when we say “contraception” or “preventing pregnancy,” too. I am not advocating for abortion in cases of rape