February 17, iStock Learn when and how your baby becomes a boy or girl. 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.
And then, between 16 and 20 weeks, testosterone levels fall until they reach the range found in early puberty by about 24 weeks. The genital ridge starts lengthening around week 9 to form the penis; however, the penis and clitoris actually remain the same size until about 14 weeks.
In your baby boy, buds that will become the prostate appear around 10 weeks. In girls, development of external sex organs remains pretty much static over time. Ovaries appear around week 11 to 12 of pregnancy. The vagina opens on the surface of the perineum at 22 weeks. That said, technicians do occasionally make the wrong call. They can mistake an umbilical cord for a penis in girls.
Women who have gestational diabetes, for example, are slightly more likely to have boys because of greater metabolic changes. And women who are extremely stressed are a bit more likely to have girls, because girls are less susceptible to unfavorable conditions in the womb. Not sure if an animal has been given hormones? Buy organic , since all organic chicken, beef and pork is guaranteed to be hormone-free. These meats are more likely be free-range as well, which ups the amount of brain-boosting omega-3 fatty acids.
If this happens, the baby may be born appearing to be female on the outside with mostly male anatomy in the inside, or with genitals that are mix of male and female types a girl born with a very large clitoris or a boy with a very small penis.
NIPT and other prenatal testing can detect this condition in utero, so you can prepare and plan accordingly.