Christ, where to even start with that premise? It's practically the default setup for a 'Fifty Shades' fic that wants to double down on the melodrama, isn't it? The biggest hurdle is making Ana feel like a person instead of just a vessel for suffering. The canon material already has her as this sort of blank slate, so piling on pregnancy and isolation risks turning her into a martyr figure readers just pity from a distance.
You've got the practical stuff, obviously—money, health, navigating a high-risk pregnancy without the billionaire safety net. But the real challenge a writer faces is the emotional logic. Why is she alone? Did Christian leave? Did she leave him? If it's the latter, you have to sell her decision to walk away from insane wealth and protection while carrying his child, which requires a spine the book-Ana rarely showed. If he left her, you're wrestling with his character, making his abandonment believable within the bounds of his canon obsession/possessiveness. It’s a tightrope walk between tragedy and outright character assassination.
Honestly, the fics that work for me are the ones that use the pregnancy as a catalyst for Ana to build something separate from him, even if it’s messy and scary. Otherwise, it just feels like an extended, soggy waiting game for Christian to swoop back in and fix everything, which gets old fast.