Weeks 23-25

The end of week 23 was an important milestone: if born and given the appropriate care, he now has a good chance of survival--about 85 percent. About 50 percent of "early preemies" experience complications ranging from eye problems to intracranial hemorrhage (spontaneous bleeding in the brain); the rate drops steadily from the 24th week onward.

The baby is growing steadily, gaining about a quarter of a pound since a week. Currently, he is about a pound and a half. Since he now measures about 13 1/2 inches, that makes a pretty lean figure, but his body is filling out proportionally and he has begun to put on baby fat. As this continues, his wrinkled skin will begin to smooth out and he'll start to look more and more like a newborn. His skin is thin, translucent, and wrinkled. Also, his brain is growing rapidly, and his taste buds are developing.

His lungs are developing "branches" of the respiratory "tree", as well as cells that produce surfactant, a fatty substance that that covers the inner lining of the air sacs and allows the lungs to expand normally so breathing can occur. Although it will be approximately 10 more weeks before the lungs are fully operational, the production of surfactant is an essential step in making the fetus viable outside the womb.

A critical component of the fetal support system is the umbilical cord, which forms a vital link between the fetus and the placenta. The cord contains two arteries and one large vein; by birth, it may measure up to four feet long. Every 30 seconds, nutrients and oxygen-rich blood are transported from the placenta to the fetus via the single vein, then back again to the placenta through the two arteries. This ingenious method ensures a constant supply of filtered air and nutrients, and keeps the mother's blood separate from the baby's.