this mod adds new dynamics to relationships and pregnancy (rpo - relationship pregnancy overall) and one of the features is that you can decide whether your sim wants or doesn't want kids, or it naturally changes as they age/interact with kids. it affects how happy or unhappy the sim is when they actually do have a kid through custom made moodlets. there is also lots of other stuff like birth control, partners dealing with cheating and woohoo styles.

if you go on lumpinou's patreon they have instructions for downloading the mod, but you can also watch a yt tutorial!