Inside Ty's body, the ineviable result of their primal, animal mating was taking hold. Even though Eileen had been a man for but a few minutes, his semen was as fertile and eager to cause reproduction as if he had been for his whole life, and once Ty's testicles had reshaped into her ovaries, the surge of hormones inside her had made them produce an ovum, awaiting fertilisation and implantation into her newformed womb.
Ty saw in her head what was occurring within her- energetic sperm found her egg and set about chewing away at its walls, and it was willingly capitulating to them, the only question being which one would reach its centre first. There wasn't a hint of conscious input into all this, only their bodies' natural instincts to seize on the opportunity to reproduce. And sure enough, one of them managed to penetrate its way into the egg's core, in response to which it slowly moved into Ty's freshly formed womb and she became pregnant.
As reality slowly irised back in for Ty, she saw Eileen sit up, his handsome dark chest before her, and slowly pull out, their combined cum covering his shaft and leaking out of her slit. Her head was still in a haze of arousal and disbelief about what he and Eileen had just done- he'd just transformed her into a man, castrated himself and allowed him to fuck her and get her pregnant with his child. And even though she knew this was impossible and wrong, it had felt so, so, SO good. She couldn't help but want to see this through.