Garcia-Falgueras Alicia, Swaab Dick F
Endocr Dev. 2010;17:22-35. doi: 10.1159/000262525. Epub 2009 Nov 24.
The fetal brain develops during the intrauterine period in the male direction through a direct action of testosterone on the developing nerve cells, or in the female direction through the absence of this hormone surge. In this way, our gender identity (the conviction of belonging to the male or female gender) and sexual orientation are programmed or organized into our brain structures when we are still in the womb. However, since sexual differentiation of the genitals takes place in the first two months of pregnancy and sexual differentiation of the brain starts in the second half of pregnancy, these two processes can be influenced independently, which may result in extreme cases in trans-sexuality. This also means that in the event of ambiguous sex at birth, the degree of masculinization of the genitals may not reflect the degree of masculinization of the brain. There is no indication that social environment after birth has an effect on gender identity or sexual orientation.
胎儿大脑在子宫内发育期间，通过睾酮对发育中的神经细胞的直接作用，朝着男性方向发展；或者在没有这种激素激增的情况下，朝着女性方向发展。这样一来，当我们还在子宫里的时候，我们的性别认同（即对属于男性或女性性别的信念）和性取向就被编入或组织进我们的大脑结构中。然而，由于生殖器的性别分化发生在怀孕的前两个月，而大脑的性别分化始于怀孕的后半期，这两个过程可以独立受到影响，在极端情况下可能导致易性癖。这也意味着，在出生时性别不明确的情况下，生殖器的男性化程度可能无法反映大脑的男性化程度。没有迹象表明出生后的社会环境会对性别认同或性取向产生影响。
