Your Baby is the Size of a Peach

Baby's intestines and vocal cords are developing

What else is going on in there? At 13 weeks pregnant, tiny bones are beginning to form in his arms and legs. Because he can move them in a jerky fashion, he may be able to get his thumb into his mouth soon — a habit that may come in handy for self-soothing when he's a newborn.

Your baby's intestines are also in for some big changes. Until recently, they've been growing in a cavity inside the umbilical cord, but they've just moved into their permanent — and more conveniently located — address, in your baby's abdomen. And to serve your growing fetus' needs, the placenta is also growing, eventually weighing 1 to 2 pounds at birth.

Also developing this week: your baby's vocal cords (the first step toward saying, "I love you, Mommy!"). You obviously can't hear him crying or cooing just yet, but you can bet that little voice will get a good workout once he's born.