How your baby’s growing:Your baby weighs 5 ounces now (about as much as a turnip), and he’s around 5 inches long. He can move his joints, and his skeleton — until now rubbery cartilage — is starting to harden to bone. His sense of hearing is also developing. 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.