First appeared in Asimov's. It was up for the Asimov's Reader Poll and reprinted by Gardner Dozois and Sheila Williams. From the collection, Sexual Chemistry and Other Tales of the Biotech Revolution.
Gerald had engulfed his twin brother when they were embryos, bobbing around in their mother's womb. As an adult, Gerald, worried about a growth, sees a doctor who tells him that he does not have a tumor but a baby that has to be carried to term. Gerald hopes he has the right to terminate. His mother, however, wants to gain control over the baby’s future as it is her child. There was only one way to win this battle, and very few of his loved ones would be pleased with the outcome.
A clever extrapolation of an idea although the desire of why “he” wanted to attain the final outcome needed development.