Does Catholicism also forbid sexual acts that cannot cause pregnancy?
If you want an answer you may have to be more specific.
If you are talking about anal or oral sex, for example, those are not permitted.
If you are talking about, for example, a sterile married couple having sex, then that is permitted.
I’ll admit, some of this can be very complicated.
Depends.
The Church requires that the sexual act be completed internally, penis in vagina.
Oral sex is permitted as foreplay, but not to the point of completion. So too with anal sex, foreplay yes, completion,no.
This is why masturbation is always wrong, there can be no natural end. (Natural in the sense that nature intended sex for reproduction)
Knowingly sexual acts that cannot result in pregnancy due to age or medical condition (wife already pregnant) are entirely acceptable because the act itself is still natural.
However, even if you and your spouse are unable to conceive, for whatever reason, it is still not morally permissable to engage in nonpotentially lifegiving sexual acts, such as oral sex to the point of completion. No matter what your reproductive status is, the sex act must alway complete internally. This is because the Church’s teachings aren’t about making as many babies as possible, although that’s how it is often misunderstood. You must always give yourself fully to your spouse, that is the only way the two become one.
It's always a little awkward to explain things like this in a general forum (where you feel you're talking about your gynecological exam in a loud voice in a Greyhound bus station) but OK, I'll explain further: you're not to deposit semen up somebody's butt, down their throat, into their shoes or pieces of beef liver or little latex balloon-thingies.
Now foreplay, and after-play, and play-play and any other kind of friskiness, is not dealt with or mentioned here, because all those thing are ad libitum ("as you like it") as long as they are muturally agreeable and not disgusting or dangerous to either party. Frisk away, by all means. But the marital act per se, can be described as either procreative or perverted in form, and procreative in form means ejaculation into the wife's vagina.
Obviously in form doesn't alwsys mean in effect. Vaginal intercourse cannot result in procreation if the woman is already pregnant,or post-menopausal, or in her infertile time (which is most of the time), or if the man hasn't a minimum count of live sperm, etc. etc. And that's all OK, if that's the way it is. Whether there is effective fertility present or not, marital intercourse is still an honorable thing and a blessing to the husband and wife.
A little rejoiceful jigging here .... :o)
And why is it so important to avoid perversion? Because it' a matter of meaning. Honest-to-God lovemaking "means" lifegiving even when it doesn't "achieve" lifegiving. Perversion has a different meaning: it means slamming the door, hard, on sanctity. Meanings are important, and meanings are embodied.
I hope that makes some sense.
Good love keeps things beautiful. It keeps intact the natural heart-to-heart delight that God intends for us. It can be expressed better, I suspect, in poetry than in doctrinal definition: as e.e. cummings said,