Exactly! I seriously do not think the loss of attraction is because he looks atrocious in heels or comes off looking like a drag queen, it's because as Humans we instinctively shy away from things that make us uncomfortable or feel dangerous. A man suddenly wanting to be a woman is BOTH of those things. Any soon-to-be mother is going to think about the well being of her coming child, and that throws up all kinds of red flags.

And, not to go all psychologist or anything, but it's VERY clear to me that his 'change' happened because his partner, as is typical of pregnant women, was likely getting far more attention and catered to than he was and it made him jealous. Plus, him suddenly being a "woman" catapulted his needs up-to or ( in his mind ) over her own. That's a dead-ringer for narcissism.