Fetal Development Weeks 9 Through 13

See what's happening with your baby in the third month of your pregnancy.

Week 9

Sometime in the last few days, the first detectable brain waves went coursing through your baby's head. What kind of thoughts might she be thinking? She's nearing an inch in length, about a big as your pinky toe.

Boy or girl? The answer to pregnancy's biggest question was actually settled seven weeks ago, at the moment the egg was fertilized when the sperm contributed either a Y chromosome, which would create a boy, or an X chromosome, which makes a girl. But until this point in its development, the embryo has had no outward signs of gender. This week, the gonads, or reproductive glands, come into being. They are the tiny beginnings of either testes or ovaries. But don't rush to get your ultrasound just yet- those tiny sex organs won't be visible for another six to eight weeks.

The baby's muscles are growing and getting stronger, and its movements are increasing. Elbows, knees, and other limb joints are distinguishable. Any day now, toenails will appear at the tips of budding toes.

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