Week Six

Baby Ticker

Week Six

How your baby's growing: The cells that will make up all of your baby's body parts and systems are dividing furiously as her body begins to take shape. Right now she's about the size of a small lentil bean (4 to 5 millimeters across).

If you could see through your uterine wall, you'd find an overlarge head and dark spots where her eyes and nostrils are beginning to take shape. Shallow pits on the sides of her head mark her developing ears, and her arms and legs appear as protruding buds. Her hands and feet look like paddles, with thick webbing between the developing digits, but her fingers and toes will soon become more distinct. Below the opening that will later be your baby's mouth, there are small folds where her neck and lower jaw will eventually develop. (Inside, her tongue and vocal cords are just beginning to form.)

Your baby's heart (which is starting to divide into the right and left chambers) is beating about 100 to 130 beats per minute — almost twice as fast as yours — and blood is beginning to circulate through her body. Her intestines are developing and tiny breathing passages are beginning to appear where her lungs will be.

She's also starting to build muscle fibers and, halfway through this week, she'll likely start moving her tiny limbs. Unfortunately, you'll probably have to wait until you're several weeks into your second trimester before you get to enjoy feeling your baby's calisthenics.