Yes all fetuses start out is female, though they are already male or female at the DNA level. Actually all fetuses start out as tadpoles more or less. The changes occur if the fetus creates certain male hormones, which sometimes doesn't happen in a baby that is male DNA wise, and sometimes does happen in a fetus that is female DNA wise.
The cells that become the clitoris in a girl, become a penis in the boy. The clitoral hood and foreskin are the same in the begining. The ovaries become the testes, and the labia the scrotum.
"Initially, all human fetuses are female, in that the default pathway is to develop into a female. During the eighth week of gestation, the presence of a Y chromosome and a functional locus for the SRY gene product, also called the testes determining factor (TDF), determines if testicular development will occur. This process converts the inherently female fetus into a male one, as a steadily increasing surge of testosterone is then produced by the testes. Much of the testosterone is converted to dihydrotestosterone, which is the key hormone to virilize the fetus. Along the biochemical pathway, other recently identified gene products likely play an additional role in the masculinization of the fetus.
Further progression toward the eventual male phenotype occurs as antimüllerian hormone is produced, inhibiting the formation of müllerian ducts, which would lead to female genital development. The fetal brain is also affected by this process. The corpus callosum, amygdala, cerebellum, and portions of the preoptic area of the hypothalamus are larger in brains exposed to testosterone. Corresponding parts of the brain are smaller in female, or testosterone-deprived, fetuses. Indeed, in the absence of testosterone, the fetus continues its progression in the female state. Development of the ovaries and the female genital tract is likely triggered by follicle-stimulating hormone (FSH), which is present in both male and female fetuses, but whose effect is masked by the testosterone surge in males.
The gender identity of a fetus, and later an infant, is still incomplete. Yet, current research indicates that because of the expected hormonal exposure secondary to genetic sex, a certain gender bias probably exists in all newborns. This rudimentary gender identity, although incomplete, is an important determinant in gender development. The dimorphism of the brain itself suggests this. Nevertheless, variations may occur when endogenous or exogenous factors create a fetal environment where hormone levels do not follow the genetically determined pattern. The gender bias of these infants may be tilted away from one that correlates with the genotype. Such variations are discussed below. "
"8th WEEK: Major organs begin development.
Now about size of hen's egg.
Embryo is 1" long and about 4 grams.
Hands and feet are seen.
Baby is extremely reactive to its environment.
Male sex hormone (testosterone) produced by testes
Masculine development in males - no change in females."
"When the genitals begin to form
Male and female genital systems are identical through the sixth week of gestation or the eighth week of your pregnancy. By week 12 to 14, your baby's external genitalia are recognizably male or female, but they're still not completely formed. On ultrasound, if your baby is cooperating and is positioned in a favorable way, his or her sex can be identified as early as the 16th to 18th week of your pregnancy. Of course, if your baby is "hiding his stuff" (positioned in such a way as to prevent identification), it will make no difference how far along in your pregnancy you are--you won't find out your baby's sex"
Sorry that's the best I can find in the time I am willing to spend doing your research for you.
· 1 decade ago