What's with those pregancy questions on so many games. It is a rather specific fetish and in my opinion should not be in most games for several reasons. Also, people asking for that and other things, usually do that on many, many games, overinflating the apparant popularity for such things.
You could do it in a visual novel that spans over long periods of time or as an ending scene.
But in normal game play it is immersive breaking. Doubly so.
Pregnancy lasts 9 months and unless you have a significant amount of time skips or magic explanation, this is not gonna happen in most games by ingame time constraints alone.
But it gets better. If you allow for pregnancy in the game world, you also should have all the surrounding real world consequences of having unprotected sex. Foremost, that most people would not do it, because they know unwanted pregnancy can happen. They would use condoms. They would have to manage birth control, and have that time of the month days. And then finally there is a baby to care for.
It is such a huge impact on any scenario that it completely changes the game. You might attract some players for the fetish, and alienate a whole bunch of others.
For me, adult games happen in the magical world of suspension of disbelief where people do not use condoms, can have anal intercourse without preparation, women do not have periods, men can always get a boner, and so on. Adding pregnancy breaks this.
That being said, if one wants to add "pregnancy" to an adult game, that would easiest be done by adding an already pregnant character. Having it involve the mc is making the game revolve about the pregnancy in some way. And that is a bad thing, if the game was not set out to be a procreation simulator in the first place.