imagining a world where pregnancy is caused when someone makes you orgasm, so a round, heavy belly is a sign of having received pleasure. people love to be seen with a pregnant partner, because in addition to all the other reasons it's hot, it's a sign that you're a generous lover.
what if, also, this is how pregnancy progresses, so that you need regular orgasms, given to you by another person, to stay on track?
too much, and you blow up way ahead of schedule, bloated with multiples. everyone will know how good you're getting it. you'll meet the friend group for dinner, clothes way too small for your swollen belly, and they'll ask who the lucky person is who made you this way, and tease you for the way you'll be even bigger when you go back home to them at the end of the night
too little, on the other hand, and you may end up knocked up but not able to progress, stuck maybe at six months pregnant for years, perhaps desperate for someone to help you reach the end. (or perhaps not-- save me, perma-pregnant service top)