Andy considered various in-between and compromise options, but in the end decided that it would be best to just fully experience girlhood. After all, even if he hated it it would only be for six months, right?
He went for the package informally referred to as "basic bitch." This was essentially what he would have been had the sperm carrying the X got to the egg before the sperm carrying the Y.
They showed him to a room with a metal tube where he was meant to stand in while he was being transformed, and he got in and took off his clothing as he was supposed to. There was something liberating about the entire idea of it, no gender whatsoever. Though as he got into the metal tube, and felt its dark walls surround him, there was a slight bit of fear that he would regret something. Though this door wouldn't open, so it was too late now...
A light came on in the tube, and he saw a graphic on a screen showing the process of fertilization- a penis ejaculating inside a vagina, and sperm surrounding an egg, one of which moved inside. It rewound like an old videotape, and this time a different sperm moved inside first. That was cute, he thought- slowly realizing it was his body he had just seen get altered at practically the first moment of his existence.
The change flowed through Andy's existence rapidly, and presently his body reshaped itself to fit her conception. He could feel his skin and bone reshaping, and see how his figure became more petite and lithe. He saw himself develop an hourglass figure, smooth skin mostly devoid of hair, and a pretty feminine face. Even his hands and feet were more dainty and small now.
Warmth emerged in his chest and crotch as his male reproductive system turned female. Mammary glands developed in his chest, and his nipples widened and perked up as soft breasts formed under them, mounds of flesh expanding outwards. He looked down and saw his penis start receding into his body, his testicles moving up inside the body and turning into feminine ovaries. His scrotum receded into his crotch, and a slit formed along its seam as a vagina developed inside before its lips emerged. Atop it his penis finished receding and became a clitoris.
Amy looked at herself in amazement at realizing she really had just turned into a girl version of herself. Once she left the tube, she took a set of clothes which had been given to her to replace her male ones, and dressed before leaving the clinic.