Week 20

"You've made it to the halfway mark — congratulations! Your baby weighs about 10 1/2 ounces now. She's around 6 1/2 inches long from head to bottom, and about 10 inches from head to heel. (For the first 20 weeks, we use measurements taken from the top of the baby's head to her bottom — known as the "crown to rump" measurement. After that, we use measurements from head to toe. This is because a baby's legs are curled up against her torso during the first half of pregnancy and are very hard to measure.)

A greasy white substance called vernix caseosa coats your baby's entire body to protect her skin during its long submersion in amniotic fluid. This slick coating will also ease the journey down the birth canal when the time comes.

Your baby is swallowing more, which is good practice for her digestive system. She's also producing meconium, a black, sticky substance that's made up of dead cells, digestive secretions, and swallowed amniotic fluid. This meconium will accumulate in her bowels, and you'll see it in her first messy diaper (although a few babies pass it in utero or during delivery)."

-- from www.babycenter.com