Week 17

From baby-gaga:
As your baby is in the middle of an impressive growth spurt it should come as not surprise to hear that they've already added nearly another inch to their length and over an ounce and a half to their weight (they're around 5 ounces and 5 inches). You're definitely feeling the growth as your belly expands enough to make you feel a bit off balance now and again. Also watch out for that round ligament pain...

From babycenter:
Your baby weighs 5 ounces now (about as much as a turnip), and he's around 5 inches long. 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.