Baby Development: Weeks 17 - 20
By the middle of the second trimester, your baby is about eight inches long and weighs half a pound. Your baby's bones are hard and the joints flexible. Now you can feel the baby's kicks and rolls. Even hiccups can be felt on occasion. Eyelashes begin to appear.
Your baby's heart pumps 144 liters of blood a day, creating enough percussion to be heard faintly through a stethoscope. Your baby's skin is loose and wrinkled, without yet a layer of fat underneath.
Your baby begins secreting vernix, the waxy coating that protects the skin from the amniotic fluid and cushions it against scratches from its own toes and fingers as it kicks and rolls. Newborns arrive coated in vernix, which is cleaned off immediately after delivery. Your baby's circulatory system is fully functional, as the umbilical cord thickens to carry liters of blood and nourishment daily from you to the baby.
Your baby is approximately 10 inches long and weighs 12 ounces. Your baby moves around a lot, but you will just begin to feel faint movements called "quickening" and maybe some hiccups, small spasms or twitching in the lower abdomen. Your baby's brain is beginning to grow rapidly during this week. If the fetus is a girl, her uterus has completely formed. If a boy, his testes will begin to descend. The hair on the baby's head is starting to appear.