The Inside Story: Your Baby in Week Twenty-One

As your baby continues to develop, she is becoming increasingly aware of your activities.

Congratulations! You're officially halfway through your pregnancy! Your baby is halfway to her birth size too, measuring an amazing 9 or 10 inches long and growing fast. It seems like she hardly ever sleeps now that she's big enough to be felt, though in reality a baby kicks only several times per hour, then sleeps for a period of time, awakens, and kicks some more. Because she still has room to move in your uterus, you'll feel the kicks in random places. At this point, it's tough to tell a foot from a fist.

As she continues to plump out, your baby will start to look like a little doll, complete with eyebrows. She's now completely covered with that white, pasty layer of vernix caseosa. Most of that substance will probably disappear before birth, except in certain places like the creases of her neck and behind her knees. Up until this point, her liver and spleen have produced nearly all of her blood cells. The liver will keep doing that until after her birth, and now her bone marrow's getting up to speed, churning out red blood cells as well.

Your baby's brain is growing as fast as the rest of her, and it will keep growing rapidly for several more years. Meanwhile, meconium is forming in her bowels--that's a blackish green, sticky substance that originates in your baby's digestive tract--and it will probably be passed through with your baby's first stool.

As your baby's senses develop, she's becoming increasingly aware of your eating and sleeping habits and of light and noise levels outside your body.

Originally published in You & Your Baby: Pregnancy.

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