Let's see what we can add; it's still in the testing phase.
Since I haven't gotten this far yet, but I'll leave ideas anyway.
The obvious one is birth, but I already mentioned the alternative if it can't be done. In any case, there could be a minigame to control their breathing or when they push or something.
We could have labor, which could be an event or series of events itself or something that happens, let's say 5-3 days before the birth event takes place. Like, maybe there's a special dialogue option for it. Maybe there are interactions where you ease the pain like having a warm bath or giving massages. Character models can even change too, like they're leaning forward a bit or they have tired eyes and their cheeks flushed.
Pregnancy interactions don't have to end at just sex. There could be more interactions like feeling the belly or hugging. Bathing together, having dinner, looking for kicks, listening for a heartbeat, sitting in the park, shopping, etc.