When is sex determined in a fetus

Various hormones, chemicals, and teratogenic agents exhibit gender-related effects in utero as well as postnatally. Among such gender-specific teratogens are endocrine disruptors, especially phthalates that affect male gonads, diabetes-induced oxidative stress with more deleterious effects on male offspring, procarbazine-induced cleft palate affecting more male fetal rats compared to females, and VPA-induced autism-like behavior that affects differently males than females. Hence, there are many needs for the accurate determination of genetic gender. In newborn animals, the morphological methods that exist for sex determination i. Hence, an accurate and simple method for the prenatal and early postnatal assessment of the genetic sex, prior to reliable evaluation from the external genitalia, is of utmost importance. Indeed, several methods have been developed for accurate assessment of genetic sex, which are discussed in this chapter.
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Sexual differentiation

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Geneticists make new discovery about how a baby's sex is determined -- ScienceDaily

One of the most exciting things about having a child is learning the gender of the baby. Many people choose to find out as soon as possible, while others decide to keep it a surprise. Although you may not see sex organs on a sonogram for weeks, a baby's sex is determined long before it arrives in the world. Gender is determined immediately upon fertilization.
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Sexual differentiation in humans

Embryos with XY chromosomes become boys, and those with XX chromosomes become girls. That means that all our sex organs come from the same foundations: The testes in men are equivalent to labia and ovaries in women, and the penis is the equivalent of the clitoris. At around week 7 , the Y chromosome signals for the start of testosterone production, and male genitalia begin to develop. Between 16 and 20 weeks, testosterone levels fall until they reach the range found in early puberty by about 24 weeks.
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NCBI Bookshelf. Sex differences of importance to health and human disease occur throughout the life span, although the specific expression of these differences varies at different stages of life. Some differences originate in events occurring in the intrauterine environment, where developmental processes differentially organize tissues for later activation in the male or female. In the prenatal period, sex determination and differentiation occur in a series of sequential processes governed by genetic and environmental factors.
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