In their aroused haste, Ty and the boy had not thought to use protection, and as the two of them slept, Ty's body continued to fulfil its newly assigned biological role. See, when Ty had turned into a girl his sperm had been bound together and transformed into an ovum, meaning she was fertile. And the boy's sperm were poised to take full advantage.
They flowed into her body en masse, and soon scores of energetic seed were eagerly weaning away her egg's walls. The egg capitulated to them rapidly in line with its biological imperative, rational considerations as dormant as the girl it belonged to- as an ovum, its task was to be fertilized, and it was surrounded by sperm that could fertilize it.
Soon one of them pushed through and reached its insides, fertilizing the ovum and starting its division and transformation into a xygote. The fertilized egg proceeded to move by instinct into Ty's womb, and implanted itself comfortably.
Ty slept soundly, not knowing how her body had adopted the most totalizing embrace of its new womanhood. When she awoke...