Week 17

Your baby weighs about 5 ounces now, and he's around 5 inches long — about the size of a large onion. The umbilical cord, his lifeline to the placenta, is growing . stronger and thicker. Your baby can move his joints, and his skeleton — until now, rubbery cartilage — is starting to harden into bone. Some of it will remain cartilage for years after he's born. A newborn's skeleton has 300 parts (a combination of bone and cartilage). As your child grows, some of these parts harden and fuse together. By the time your baby reaches adulthood, he'll have just 206 bones.