Good story! I liked the overall premise, it all hangs together pretty well.
I enjoyed the "soft machine" of the pod. At points I wondered if it was really a manufactured device, or a piece of bio-engineering that had been "grown" rather than "constructed." I think it works either way.
Many small elements like the stretching of Sara's body by the pod, the milking, and especially the electrically-induced contractions were all nicely done! With the use of drugs there's a good balance between sedation/pain suppression and awareness/sensation. Also a nice job communicating Sara's thoughts and sensations.
I most enjoyed the body modification elements; the "bone flexibility enhancers" and expansion of her pelvis for example. I'd have liked more detail on the body modification.
Also, you might have added a little element of deception at the beginning by whoever administers the program, so Sara's surprise at the end makes more sense.
Good work, and I hope to see more sci-fi impregnantion/breeding stuff - consent optional!
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Benfan
