Can I remind people that trans people are not just MTF but also FTM.
Also I've said it before, and no doubt I'll say it again. The parents are not denying the child a sex. They are denying the world the right to put a label on how the child acts. Society has built this perception of gender up to such a height that it has become the single most important thing to us. We would be horrified if someone claimed that skin colour or race meant that we should do certain jobs and behave in certain ways. Why do we think it's okay to do it by gender?
Instead of assigning a list of characteristics to men, and a list to women and claiming there is no crossover, how about we posit the new and exciting idea (!) that we're all people. And that shock!horror! some girls possess qualities that we think of masculine and vice versa.
What people forget, is that if we lived in a world where gender didn't matter, when it came to what you played with, what job you had, how you were treated by people around you, EVERYONE would be happier. They really would. Because gender roles don't just harm girls, they harm boys as well, and they can damage children in ways we don't even know about.
I firmly think that in a centuries time, our descendents will look back at us, and be horrified by our society. There'll probably be students saying 'so if I was born with a vagina in the 21st century, it would affect every single thing about my life, including how I was treated, how I was expected to behave, and my gender identity. How absolutely awful.' And another one saying 'the fact I was born with a penis, would've meant that I too was forced into behaving in a certain way, and if I stepped out of line would be subjected to ridicule and insults against my supposed masculinity.'