Week 17 5.1 in 5.9 oz M's skeleton is changing from soft cartilage to bone, and the umbilical cord — the lifeline to the placenta — is growing stronger and thicker. Fat is also finally starting to accumulate around the baby. Baby M weighs about 5 ounces now (about as much as a turnip or onion), and M's around 5 inches long from head to bottom. Can move joints, and the sweat glands are starting to develop. Baby M's little fingers and toes are now topped by one-of-a-kind prints.