Month 5: Weeks 17 to 20
The baby is about 9 inches long and weighs about 8 ounces, but in the next few weeks the baby will double his weight. Glands in the skin begin to produce a greasy material called vernix. This material acts as a waterproof barrier that protects the baby’s skin. The skin will be completely covered with this material by the time the baby is born.
Your baby sleeps and wakes regularly and now can be awakened from sleep by noises and your movements. Soft, downy hair, called lanugo, is starting to form and will cover your baby’s body. This hair helps keep your baby warm inside the womb. In girls, ovaries containing eggs have formed, and in boys, the testes have begun to descend.
Your baby’s kicks and turns are stronger now. If you have already felt your baby move, the movements are more noticeable now. The sucking reflex is developing. If your baby’s hand floats to his mouth, he may suck his thumb.
Your baby may weigh as much as 1 pound now, and he is about 10 inches long. He is swallowing more often. He also is producing meconium, a greenish black, sticky by-product of digestion. This substance will accumulate in his bowels, and you’ll see it in his first soiled diaper (some babies pass meconium in the womb or during delivery). Your baby’s nails grow to the ends of the fingers and may get so long that they will need to be trimmed once he is born.