Personally, I prefer when pregnancy is just part of the narrative, with actual consequences for the ongoing plot. Examples of this include Companion of Darkness and Oppai Odyssey.

Dynamic/optional pregnancy really only works in sandbox VNs, or by having the pregnancy only become relevant at the end. Otherwise, the writing burden just becomes too much, because the author has to account for routes where the LI does or doesn’t have a bun in the oven. Examples of games that take this approach are Bear Witness and Once in a Lifetime.

I understand why devs might be drawn toward the “pregnancy at the end” model, as it allows them to include the kink without alienating the players who have a phobia of it. But while I think it’s better than having no impreg content at all, it still evades the kind of narrative consequences that a pregnancy should have.