WebMD:
Your baby measures about 18.9 inches long from head to toe and weighs almost 4 pounds. It fills almost all the space in your uterus now. A layer of fat is forming underneath the thin, wrinkly skin. Baby’s practicing opening his eyes and breathing. Most internal systems are well developed, but the lungs may still be immature. You may continue to get backaches and leg cramps and you may notice colostrum—a yellowish fluid that precedes milk production—leaking from your breasts.