I remember reading a story. It's about a woman who wants to be a model but couldn't because it was maternity themed. So her idol sends her these pills that allows her to unbirth her friend, the instructions are for her to take two blue pills and her friend to take two yellow pills, they also have to be in a body of water and to wait 10 minutes. There's a whole sequence describing the unbirthing in a hot tub, like the friend de-ages into a fetus.

After the shoot, the pregnant woman than takes two purple pills that would allow her to birth her friend. She gives birth in a bathtub and while she nurses her friend, the friend rapidly ages into their proper age and that's how far I got into the story. I remember reading this story on DeviantArt. If anyone knows what story I'm talking about, please send me a link.